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256 commits
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e9e9b7ecee |
mm: swap: unify cluster-based and vma-based swap readahead
This patch makes do_swap_page() not need to be aware of two different swap readahead algorithms. Just unify cluster-based and vma-based readahead function call. Link: http://lkml.kernel.org/r/1509520520-32367-3-git-send-email-minchan@kernel.org Link: http://lkml.kernel.org/r/20180220085249.151400-3-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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eaf649ebc3 |
mm: swap: clean up swap readahead
When I see recent change of swap readahead, I am very unhappy about current code structure which diverges two swap readahead algorithm in do_swap_page. This patch is to clean it up. Main motivation is that fault handler doesn't need to be aware of readahead algorithms but just should call swapin_readahead. As first step, this patch cleans up a little bit but not perfect (I just separate for review easier) so next patch will make the goal complete. [minchan@kernel.org: do not check readahead flag with THP anon] Link: http://lkml.kernel.org/r/874lm83zho.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20180227232611.169883-1-minchan@kernel.org Link: http://lkml.kernel.org/r/1509520520-32367-2-git-send-email-minchan@kernel.org Link: http://lkml.kernel.org/r/20180220085249.151400-2-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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9c4e6b1a70 |
mm, mlock, vmscan: no more skipping pagevecs
When a thread mlocks an address space backed either by file pages which are currently not present in memory or swapped out anon pages (not in swapcache), a new page is allocated and added to the local pagevec (lru_add_pvec), I/O is triggered and the thread then sleeps on the page. On I/O completion, the thread can wake on a different CPU, the mlock syscall will then sets the PageMlocked() bit of the page but will not be able to put that page in unevictable LRU as the page is on the pagevec of a different CPU. Even on drain, that page will go to evictable LRU because the PageMlocked() bit is not checked on pagevec drain. The page will eventually go to right LRU on reclaim but the LRU stats will remain skewed for a long time. This patch puts all the pages, even unevictable, to the pagevecs and on the drain, the pages will be added on their LRUs correctly by checking their evictability. This resolves the mlocked pages on pagevec of other CPUs issue because when those pagevecs will be drained, the mlocked file pages will go to unevictable LRU. Also this makes the race with munlock easier to resolve because the pagevec drains happen in LRU lock. However there is still one place which makes a page evictable and does PageLRU check on that page without LRU lock and needs special attention. TestClearPageMlocked() and isolate_lru_page() in clear_page_mlock(). #0: __pagevec_lru_add_fn #1: clear_page_mlock SetPageLRU() if (!TestClearPageMlocked()) return smp_mb() // <--required // inside does PageLRU if (!PageMlocked()) if (isolate_lru_page()) move to evictable LRU putback_lru_page() else move to unevictable LRU In '#1', TestClearPageMlocked() provides full memory barrier semantics and thus the PageLRU check (inside isolate_lru_page) can not be reordered before it. In '#0', without explicit memory barrier, the PageMlocked() check can be reordered before SetPageLRU(). If that happens, '#0' can put a page in unevictable LRU and '#1' might have just cleared the Mlocked bit of that page but fails to isolate as PageLRU fails as '#0' still hasn't set PageLRU bit of that page. That page will be stranded on the unevictable LRU. There is one (good) side effect though. Without this patch, the pages allocated for System V shared memory segment are added to evictable LRUs even after shmctl(SHM_LOCK) on that segment. This patch will correctly put such pages to unevictable LRU. Link: http://lkml.kernel.org/r/20171121211241.18877-1-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Greg Thelen <gthelen@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Shaohua Li <shli@fb.com> Cc: Jan Kara <jack@suse.cz> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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a4ef876841 |
mm: remove unused pgdat_reclaimable_pages()
Remove unused function pgdat_reclaimable_pages() and node_page_state_snapshot() which becomes unused as well. Link: http://lkml.kernel.org/r/20171122094416.26019-1-jack@suse.cz Signed-off-by: Jan Kara <jack@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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9852a72123 |
mm: drop hotplug lock from lru_add_drain_all()
Pulling cpu hotplug locks inside the mm core function like
lru_add_drain_all just asks for problems and the recent lockdep splat
[1] just proves this. While the usage in that particular case might be
wrong we should avoid the locking as lru_add_drain_all() is used in many
places. It seems that this is not all that hard to achieve actually.
We have done the same thing for drain_all_pages which is analogous by
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c6f92f9fbe |
mm: remove cold parameter for release_pages
All callers of release_pages claim the pages being released are cache hot. As no one cares about the hotness of pages being released to the allocator, just ditch the parameter. No performance impact is expected as the overhead is marginal. The parameter is removed simply because it is a bit stupid to have a useless parameter copied everywhere. Link: http://lkml.kernel.org/r/20171018075952.10627-7-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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c7df8ad291 |
mm, truncate: do not check mapping for every page being truncated
During truncation, the mapping has already been checked for shmem and dax so it's known that workingset_update_node is required. This patch avoids the checks on mapping for each page being truncated. In all other cases, a lookup helper is used to determine if workingset_update_node() needs to be called. The one danger is that the API is slightly harder to use as calling workingset_update_node directly without checking for dax or shmem mappings could lead to surprises. However, the API rarely needs to be used and hopefully the comment is enough to give people the hint. sparsetruncate (tiny) 4.14.0-rc4 4.14.0-rc4 oneirq-v1r1 pickhelper-v1r1 Min Time 141.00 ( 0.00%) 140.00 ( 0.71%) 1st-qrtle Time 142.00 ( 0.00%) 141.00 ( 0.70%) 2nd-qrtle Time 142.00 ( 0.00%) 142.00 ( 0.00%) 3rd-qrtle Time 143.00 ( 0.00%) 143.00 ( 0.00%) Max-90% Time 144.00 ( 0.00%) 144.00 ( 0.00%) Max-95% Time 147.00 ( 0.00%) 145.00 ( 1.36%) Max-99% Time 195.00 ( 0.00%) 191.00 ( 2.05%) Max Time 230.00 ( 0.00%) 205.00 ( 10.87%) Amean Time 144.37 ( 0.00%) 143.82 ( 0.38%) Stddev Time 10.44 ( 0.00%) 9.00 ( 13.74%) Coeff Time 7.23 ( 0.00%) 6.26 ( 13.41%) Best99%Amean Time 143.72 ( 0.00%) 143.34 ( 0.26%) Best95%Amean Time 142.37 ( 0.00%) 142.00 ( 0.26%) Best90%Amean Time 142.19 ( 0.00%) 141.85 ( 0.24%) Best75%Amean Time 141.92 ( 0.00%) 141.58 ( 0.24%) Best50%Amean Time 141.69 ( 0.00%) 141.31 ( 0.27%) Best25%Amean Time 141.38 ( 0.00%) 140.97 ( 0.29%) As you'd expect, the gain is marginal but it can be detected. The differences in bonnie are all within the noise which is not surprising given the impact on the microbenchmark. radix_tree_update_node_t is a callback for some radix operations that optionally passes in a private field. The only user of the callback is workingset_update_node and as it no longer requires a mapping, the private field is removed. Link: http://lkml.kernel.org/r/20171018075952.10627-3-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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aa8d22a11d |
mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no other reference
When SWP_SYNCHRONOUS_IO swapped-in pages are shared by several processes, it can cause unnecessary memory wastage by skipping swap cache. Because, with swapin fault by read, they could share a page if the page were in swap cache. Thus, it avoids allocating same content new pages. This patch makes the swapcache skipping work only if the swap pte is non-sharable. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1507620825-5537-1-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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0bcac06f27 |
mm, swap: skip swapcache for swapin of synchronous device
With fast swap storage, the platforms want to use swap more aggressively and swap-in is crucial to application latency. The rw_page() based synchronous devices like zram, pmem and btt are such fast storage. When I profile swapin performance with zram lz4 decompress test, S/W overhead is more than 70%. Maybe, it would be bigger in nvdimm. This patch aims to reduce swap-in latency by skipping swapcache if the swap device is synchronous device like rw_page based device. It enhances 45% my swapin test(5G sequential swapin, no readahead, from 2.41sec to 1.64sec). Link: http://lkml.kernel.org/r/1505886205-9671-5-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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539a6fea7f |
mm, swap: introduce SWP_SYNCHRONOUS_IO
If rw-page based fast storage is used for swap devices, we need to detect it to enhance swap IO operations. This patch is preparation for optimizing of swap-in operation with next patch. Link: http://lkml.kernel.org/r/1505886205-9671-4-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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2628bd6fc0 |
mm, swap: fix race between swap count continuation operations
One page may store a set of entries of the sis->swap_map
(swap_info_struct->swap_map) in multiple swap clusters.
If some of the entries has sis->swap_map[offset] > SWAP_MAP_MAX,
multiple pages will be used to store the set of entries of the
sis->swap_map. And the pages are linked with page->lru. This is called
swap count continuation. To access the pages which store the set of
entries of the sis->swap_map simultaneously, previously, sis->lock is
used. But to improve the scalability of __swap_duplicate(), swap
cluster lock may be used in swap_count_continued() now. This may race
with add_swap_count_continuation() which operates on a nearby swap
cluster, in which the sis->swap_map entries are stored in the same page.
The race can cause wrong swap count in practice, thus cause unfreeable
swap entries or software lockup, etc.
To fix the race, a new spin lock called cont_lock is added to struct
swap_info_struct to protect the swap count continuation page list. This
is a lock at the swap device level, so the scalability isn't very well.
But it is still much better than the original sis->lock, because it is
only acquired/released when swap count continuation is used. Which is
considered rare in practice. If it turns out that the scalability
becomes an issue for some workloads, we can split the lock into some
more fine grained locks.
Link: http://lkml.kernel.org/r/20171017081320.28133-1-ying.huang@intel.com
Fixes:
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b24413180f |
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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5042db43cc |
mm/ZONE_DEVICE: new type of ZONE_DEVICE for unaddressable memory
HMM (heterogeneous memory management) need struct page to support migration from system main memory to device memory. Reasons for HMM and migration to device memory is explained with HMM core patch. This patch deals with device memory that is un-addressable memory (ie CPU can not access it). Hence we do not want those struct page to be manage like regular memory. That is why we extend ZONE_DEVICE to support different types of memory. A persistent memory type is define for existing user of ZONE_DEVICE and a new device un-addressable type is added for the un-addressable memory type. There is a clear separation between what is expected from each memory type and existing user of ZONE_DEVICE are un-affected by new requirement and new use of the un-addressable type. All specific code path are protect with test against the memory type. Because memory is un-addressable we use a new special swap type for when a page is migrated to device memory (this reduces the number of maximum swap file). The main two additions beside memory type to ZONE_DEVICE is two callbacks. First one, page_free() is call whenever page refcount reach 1 (which means the page is free as ZONE_DEVICE page never reach a refcount of 0). This allow device driver to manage its memory and associated struct page. The second callback page_fault() happens when there is a CPU access to an address that is back by a device page (which are un-addressable by the CPU). This callback is responsible to migrate the page back to system main memory. Device driver can not block migration back to system memory, HMM make sure that such page can not be pin into device memory. If device is in some error condition and can not migrate memory back then a CPU page fault to device memory should end with SIGBUS. [arnd@arndb.de: fix warning] Link: http://lkml.kernel.org/r/20170823133213.712917-1-arnd@arndb.de Link: http://lkml.kernel.org/r/20170817000548.32038-8-jglisse@redhat.com Signed-off-by: Jérôme Glisse <jglisse@redhat.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Nellans <dnellans@nvidia.com> Cc: Evgeny Baskakov <ebaskakov@nvidia.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mark Hairgrove <mhairgrove@nvidia.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Sherry Cheung <SCheung@nvidia.com> Cc: Subhash Gutti <sgutti@nvidia.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Bob Liu <liubo95@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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a2468cc9bf |
swap: choose swap device according to numa node
If the system has more than one swap device and swap device has the node information, we can make use of this information to decide which swap device to use in get_swap_pages() to get better performance. The current code uses a priority based list, swap_avail_list, to decide which swap device to use and if multiple swap devices share the same priority, they are used round robin. This patch changes the previous single global swap_avail_list into a per-numa-node list, i.e. for each numa node, it sees its own priority based list of available swap devices. Swap device's priority can be promoted on its matching node's swap_avail_list. The current swap device's priority is set as: user can set a >=0 value, or the system will pick one starting from -1 then downwards. The priority value in the swap_avail_list is the negated value of the swap device's due to plist being sorted from low to high. The new policy doesn't change the semantics for priority >=0 cases, the previous starting from -1 then downwards now becomes starting from -2 then downwards and -1 is reserved as the promoted value. Take 4-node EX machine as an example, suppose 4 swap devices are available, each sit on a different node: swapA on node 0 swapB on node 1 swapC on node 2 swapD on node 3 After they are all swapped on in the sequence of ABCD. Current behaviour: their priorities will be: swapA: -1 swapB: -2 swapC: -3 swapD: -4 And their position in the global swap_avail_list will be: swapA -> swapB -> swapC -> swapD prio:1 prio:2 prio:3 prio:4 New behaviour: their priorities will be(note that -1 is skipped): swapA: -2 swapB: -3 swapC: -4 swapD: -5 And their positions in the 4 swap_avail_lists[nid] will be: swap_avail_lists[0]: /* node 0's available swap device list */ swapA -> swapB -> swapC -> swapD prio:1 prio:3 prio:4 prio:5 swap_avali_lists[1]: /* node 1's available swap device list */ swapB -> swapA -> swapC -> swapD prio:1 prio:2 prio:4 prio:5 swap_avail_lists[2]: /* node 2's available swap device list */ swapC -> swapA -> swapB -> swapD prio:1 prio:2 prio:3 prio:5 swap_avail_lists[3]: /* node 3's available swap device list */ swapD -> swapA -> swapB -> swapC prio:1 prio:2 prio:3 prio:4 To see the effect of the patch, a test that starts N process, each mmap a region of anonymous memory and then continually write to it at random position to trigger both swap in and out is used. On a 2 node Skylake EP machine with 64GiB memory, two 170GB SSD drives are used as swap devices with each attached to a different node, the result is: runtime=30m/processes=32/total test size=128G/each process mmap region=4G kernel throughput vanilla 13306 auto-binding 15169 +14% runtime=30m/processes=64/total test size=128G/each process mmap region=2G kernel throughput vanilla 11885 auto-binding 14879 +25% [aaron.lu@intel.com: v2] Link: http://lkml.kernel.org/r/20170814053130.GD2369@aaronlu.sh.intel.com Link: http://lkml.kernel.org/r/20170816024439.GA10925@aaronlu.sh.intel.com [akpm@linux-foundation.org: use kmalloc_array()] Link: http://lkml.kernel.org/r/20170814053130.GD2369@aaronlu.sh.intel.com Link: http://lkml.kernel.org/r/20170816024439.GA10925@aaronlu.sh.intel.com Signed-off-by: Aaron Lu <aaron.lu@intel.com> Cc: "Chen, Tim C" <tim.c.chen@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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81a0298bdf |
mm, swap: don't use VMA based swap readahead if HDD is used as swap
VMA based swap readahead will readahead the virtual pages that is continuous in the virtual address space. While the original swap readahead will readahead the swap slots that is continuous in the swap device. Although VMA based swap readahead is more correct for the swap slots to be readahead, it will trigger more small random readings, which may cause the performance of HDD (hard disk) to degrade heavily, and may finally exceed the benefit. To avoid the issue, in this patch, if the HDD is used as swap, the VMA based swap readahead will be disabled, and the original swap readahead will be used instead. Link: http://lkml.kernel.org/r/20170807054038.1843-6-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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ec560175c0 |
mm, swap: VMA based swap readahead
The swap readahead is an important mechanism to reduce the swap in latency. Although pure sequential memory access pattern isn't very popular for anonymous memory, the space locality is still considered valid. In the original swap readahead implementation, the consecutive blocks in swap device are readahead based on the global space locality estimation. But the consecutive blocks in swap device just reflect the order of page reclaiming, don't necessarily reflect the access pattern in virtual memory. And the different tasks in the system may have different access patterns, which makes the global space locality estimation incorrect. In this patch, when page fault occurs, the virtual pages near the fault address will be readahead instead of the swap slots near the fault swap slot in swap device. This avoid to readahead the unrelated swap slots. At the same time, the swap readahead is changed to work on per-VMA from globally. So that the different access patterns of the different VMAs could be distinguished, and the different readahead policy could be applied accordingly. The original core readahead detection and scaling algorithm is reused, because it is an effect algorithm to detect the space locality. The test and result is as follow, Common test condition ===================== Test Machine: Xeon E5 v3 (2 sockets, 72 threads, 32G RAM) Swap device: NVMe disk Micro-benchmark with combined access pattern ============================================ vm-scalability, sequential swap test case, 4 processes to eat 50G virtual memory space, repeat the sequential memory writing until 300 seconds. The first round writing will trigger swap out, the following rounds will trigger sequential swap in and out. At the same time, run vm-scalability random swap test case in background, 8 processes to eat 30G virtual memory space, repeat the random memory write until 300 seconds. This will trigger random swap-in in the background. This is a combined workload with sequential and random memory accessing at the same time. The result (for sequential workload) is as follow, Base Optimized ---- --------- throughput 345413 KB/s 414029 KB/s (+19.9%) latency.average 97.14 us 61.06 us (-37.1%) latency.50th 2 us 1 us latency.60th 2 us 1 us latency.70th 98 us 2 us latency.80th 160 us 2 us latency.90th 260 us 217 us latency.95th 346 us 369 us latency.99th 1.34 ms 1.09 ms ra_hit% 52.69% 99.98% The original swap readahead algorithm is confused by the background random access workload, so readahead hit rate is lower. The VMA-base readahead algorithm works much better. Linpack ======= The test memory size is bigger than RAM to trigger swapping. Base Optimized ---- --------- elapsed_time 393.49 s 329.88 s (-16.2%) ra_hit% 86.21% 98.82% The score of base and optimized kernel hasn't visible changes. But the elapsed time reduced and readahead hit rate improved, so the optimized kernel runs better for startup and tear down stages. And the absolute value of readahead hit rate is high, shows that the space locality is still valid in some practical workloads. Link: http://lkml.kernel.org/r/20170807054038.1843-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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c41f012ade |
mm: rename global_page_state to global_zone_page_state
global_page_state is error prone as a recent bug report pointed out [1]. It only returns proper values for zone based counters as the enum it gets suggests. We already have global_node_page_state so let's rename global_page_state to global_zone_page_state to be more explicit here. All existing users seems to be correct: $ git grep "global_page_state(NR_" | sed 's@.*(\(NR_[A-Z_]*\)).*@\1@' | sort | uniq -c 2 NR_BOUNCE 2 NR_FREE_CMA_PAGES 11 NR_FREE_PAGES 1 NR_KERNEL_STACK_KB 1 NR_MLOCK 2 NR_PAGETABLE This patch shouldn't introduce any functional change. [1] http://lkml.kernel.org/r/201707260628.v6Q6SmaS030814@www262.sakura.ne.jp Link: http://lkml.kernel.org/r/20170801134256.5400-2-hannes@cmpxchg.org Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Cc: Josef Bacik <josef@toxicpanda.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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59807685a7 |
mm, THP, swap: support splitting THP for THP swap out
After adding swapping out support for THP (Transparent Huge Page), it is possible that a THP in swap cache (partly swapped out) need to be split. To split such a THP, the swap cluster backing the THP need to be split too, that is, the CLUSTER_FLAG_HUGE flag need to be cleared for the swap cluster. The patch implemented this. And because the THP swap writing needs the THP keeps as huge page during writing. The PageWriteback flag is checked before splitting. Link: http://lkml.kernel.org/r/20170724051840.2309-8-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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ba3c4ce6de |
mm, THP, swap: make reuse_swap_page() works for THP swapped out
After supporting to delay THP (Transparent Huge Page) splitting after swapped out, it is possible that some page table mappings of the THP are turned into swap entries. So reuse_swap_page() need to check the swap count in addition to the map count as before. This patch done that. In the huge PMD write protect fault handler, in addition to the page map count, the swap count need to be checked too, so the page lock need to be acquired too when calling reuse_swap_page() in addition to the page table lock. [ying.huang@intel.com: silence a compiler warning] Link: http://lkml.kernel.org/r/87bmnzizjy.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20170724051840.2309-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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e07098294a |
mm, THP, swap: support to reclaim swap space for THP swapped out
The normal swap slot reclaiming can be done when the swap count reaches SWAP_HAS_CACHE. But for the swap slot which is backing a THP, all swap slots backing one THP must be reclaimed together, because the swap slot may be used again when the THP is swapped out again later. So the swap slots backing one THP can be reclaimed together when the swap count for all swap slots for the THP reached SWAP_HAS_CACHE. In the patch, the functions to check whether the swap count for all swap slots backing one THP reached SWAP_HAS_CACHE are implemented and used when checking whether a swap slot can be reclaimed. To make it easier to determine whether a swap slot is backing a THP, a new swap cluster flag named CLUSTER_FLAG_HUGE is added to mark a swap cluster which is backing a THP (Transparent Huge Page). Because THP swap in as a whole isn't supported now. After deleting the THP from the swap cache (for example, swapping out finished), the CLUSTER_FLAG_HUGE flag will be cleared. So that, the normal pages inside THP can be swapped in individually. [ying.huang@intel.com: fix swap_page_trans_huge_swapped on HDD] Link: http://lkml.kernel.org/r/874ltsm0bi.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20170724051840.2309-3-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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a47fed5b5b |
mm: swap: provide lru_add_drain_all_cpuslocked()
The rework of the cpu hotplug locking unearthed potential deadlocks with the memory hotplug locking code. The solution for these is to rework the memory hotplug locking code as well and take the cpu hotplug lock before the memory hotplug lock in mem_hotplug_begin(), but this will cause a recursive locking of the cpu hotplug lock when the memory hotplug code calls lru_add_drain_all(). Split out the inner workings of lru_add_drain_all() into lru_add_drain_all_cpuslocked() so this function can be invoked from the memory hotplug code with the cpu hotplug lock held. Link: http://lkml.kernel.org/r/20170704093421.419329357@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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23955622ff |
swap: add block io poll in swapin path
For fast flash disk, async IO could introduce overhead because of context switch. block-mq now supports IO poll, which improves performance and latency a lot. swapin is a good place to use this technique, because the task is waiting for the swapin page to continue execution. In my virtual machine, directly read 4k data from a NVMe with iopoll is about 60% better than that without poll. With iopoll support in swapin patch, my microbenchmark (a task does random memory write) is about 10%~25% faster. CPU utilization increases a lot though, 2x and even 3x CPU utilization. This will depend on disk speed. While iopoll in swapin isn't intended for all usage cases, it's a win for latency sensistive workloads with high speed swap disk. block layer has knob to control poll in runtime. If poll isn't enabled in block layer, there should be no noticeable change in swapin. I got a chance to run the same test in a NVMe with DRAM as the media. In simple fio IO test, blkpoll boosts 50% performance in single thread test and ~20% in 8 threads test. So this is the base line. In above swap test, blkpoll boosts ~27% performance in single thread test. blkpoll uses 2x CPU time though. If we enable hybid polling, the performance gain has very slight drop but CPU time is only 50% worse than that without blkpoll. Also we can adjust parameter of hybid poll, with it, the CPU time penality is reduced further. In 8 threads test, blkpoll doesn't help though. The performance is similar to that without blkpoll, but cpu utilization is similar too. There is lock contention in swap path. The cpu time spending on blkpoll isn't high. So overall, blkpoll swapin isn't worse than that without it. The swapin readahead might read several pages in in the same time and form a big IO request. Since the IO will take longer time, it doesn't make sense to do poll, so the patch only does iopoll for single page swapin. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/070c3c3e40b711e7b1390002c991e86a-b5408f0@7511894063d3764ff01ea8111f5a004d7dd700ed078797c204a24e620ddb965c Signed-off-by: Shaohua Li <shli@fb.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Jens Axboe <axboe@fb.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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0f0746589e |
mm, THP, swap: move anonymous THP split logic to vmscan
The add_to_swap aims to allocate swap_space(ie, swap slot and swapcache) so if it fails due to lack of space in case of THP or something(hdd swap but tries THP swapout) *caller* rather than add_to_swap itself should split the THP page and retry it with base page which is more natural. Link: http://lkml.kernel.org/r/20170515112522.32457-4-ying.huang@intel.com Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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75f6d6d29a |
mm, THP, swap: unify swap slot free functions to put_swap_page
Now, get_swap_page takes struct page and allocates swap space according to page size(ie, normal or THP) so it would be more cleaner to introduce put_swap_page which is a counter function of get_swap_page. Then, it calls right swap slot free function depending on page's size. [ying.huang@intel.com: minor cleanup and fix] Link: http://lkml.kernel.org/r/20170515112522.32457-3-ying.huang@intel.com Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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38d8b4e6bd |
mm, THP, swap: delay splitting THP during swap out
Patch series "THP swap: Delay splitting THP during swapping out", v11. This patchset is to optimize the performance of Transparent Huge Page (THP) swap. Recently, the performance of the storage devices improved so fast that we cannot saturate the disk bandwidth with single logical CPU when do page swap out even on a high-end server machine. Because the performance of the storage device improved faster than that of single logical CPU. And it seems that the trend will not change in the near future. On the other hand, the THP becomes more and more popular because of increased memory size. So it becomes necessary to optimize THP swap performance. The advantages of the THP swap support include: - Batch the swap operations for the THP to reduce lock acquiring/releasing, including allocating/freeing the swap space, adding/deleting to/from the swap cache, and writing/reading the swap space, etc. This will help improve the performance of the THP swap. - The THP swap space read/write will be 2M sequential IO. It is particularly helpful for the swap read, which are usually 4k random IO. This will improve the performance of the THP swap too. - It will help the memory fragmentation, especially when the THP is heavily used by the applications. The 2M continuous pages will be free up after THP swapping out. - It will improve the THP utilization on the system with the swap turned on. Because the speed for khugepaged to collapse the normal pages into the THP is quite slow. After the THP is split during the swapping out, it will take quite long time for the normal pages to collapse back into the THP after being swapped in. The high THP utilization helps the efficiency of the page based memory management too. There are some concerns regarding THP swap in, mainly because possible enlarged read/write IO size (for swap in/out) may put more overhead on the storage device. To deal with that, the THP swap in should be turned on only when necessary. For example, it can be selected via "always/never/madvise" logic, to be turned on globally, turned off globally, or turned on only for VMA with MADV_HUGEPAGE, etc. This patchset is the first step for the THP swap support. The plan is to delay splitting THP step by step, finally avoid splitting THP during the THP swapping out and swap out/in the THP as a whole. As the first step, in this patchset, the splitting huge page is delayed from almost the first step of swapping out to after allocating the swap space for the THP and adding the THP into the swap cache. This will reduce lock acquiring/releasing for the locks used for the swap cache management. With the patchset, the swap out throughput improves 15.5% (from about 3.73GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case with 8 processes. The test is done on a Xeon E5 v3 system. The swap device used is a RAM simulated PMEM (persistent memory) device. To test the sequential swapping out, the test case creates 8 processes, which sequentially allocate and write to the anonymous pages until the RAM and part of the swap device is used up. This patch (of 5): In this patch, splitting huge page is delayed from almost the first step of swapping out to after allocating the swap space for the THP (Transparent Huge Page) and adding the THP into the swap cache. This will batch the corresponding operation, thus improve THP swap out throughput. This is the first step for the THP swap optimization. The plan is to delay splitting the THP step by step and avoid splitting the THP finally. In this patch, one swap cluster is used to hold the contents of each THP swapped out. So, the size of the swap cluster is changed to that of the THP (Transparent Huge Page) on x86_64 architecture (512). For other architectures which want such THP swap optimization, ARCH_USES_THP_SWAP_CLUSTER needs to be selected in the Kconfig file for the architecture. In effect, this will enlarge swap cluster size by 2 times on x86_64. Which may make it harder to find a free cluster when the swap space becomes fragmented. So that, this may reduce the continuous swap space allocation and sequential write in theory. The performance test in 0day shows no regressions caused by this. In the future of THP swap optimization, some information of the swapped out THP (such as compound map count) will be recorded in the swap_cluster_info data structure. The mem cgroup swap accounting functions are enhanced to support charge or uncharge a swap cluster backing a THP as a whole. The swap cluster allocate/free functions are added to allocate/free a swap cluster for a THP. A fair simple algorithm is used for swap cluster allocation, that is, only the first swap device in priority list will be tried to allocate the swap cluster. The function will fail if the trying is not successful, and the caller will fallback to allocate a single swap slot instead. This works good enough for normal cases. If the difference of the number of the free swap clusters among multiple swap devices is significant, it is possible that some THPs are split earlier than necessary. For example, this could be caused by big size difference among multiple swap devices. The swap cache functions is enhanced to support add/delete THP to/from the swap cache as a set of (HPAGE_PMD_NR) sub-pages. This may be enhanced in the future with multi-order radix tree. But because we will split the THP soon during swapping out, that optimization doesn't make much sense for this first step. The THP splitting functions are enhanced to support to split THP in swap cache during swapping out. The page lock will be held during allocating the swap cluster, adding the THP into the swap cache and splitting the THP. So in the code path other than swapping out, if the THP need to be split, the PageSwapCache(THP) will be always false. The swap cluster is only available for SSD, so the THP swap optimization in this patchset has no effect for HDD. [ying.huang@intel.com: fix two issues in THP optimize patch] Link: http://lkml.kernel.org/r/87k25ed8zo.fsf@yhuang-dev.intel.com [hannes@cmpxchg.org: extensive cleanups and simplifications, reduce code size] Link: http://lkml.kernel.org/r/20170515112522.32457-2-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Suggested-by: Andrew Morton <akpm@linux-foundation.org> [for config option] Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> [for changes in huge_memory.c and huge_mm.h] Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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df6b749980 |
mm, swap: remove unused function prototype
This is a code cleanup patch, no functionality changes. There are 2 unused function prototype in swap.h, they are removed. Link: http://lkml.kernel.org/r/20170405071017.23677-1-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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f7ad2a6cb9 |
mm: move MADV_FREE pages into LRU_INACTIVE_FILE list
madv()'s MADV_FREE indicate pages are 'lazyfree'. They are still anonymous pages, but they can be freed without pageout. To distinguish these from normal anonymous pages, we clear their SwapBacked flag. MADV_FREE pages could be freed without pageout, so they pretty much like used once file pages. For such pages, we'd like to reclaim them once there is memory pressure. Also it might be unfair reclaiming MADV_FREE pages always before used once file pages and we definitively want to reclaim the pages before other anonymous and file pages. To speed up MADV_FREE pages reclaim, we put the pages into LRU_INACTIVE_FILE list. The rationale is LRU_INACTIVE_FILE list is tiny nowadays and should be full of used once file pages. Reclaiming MADV_FREE pages will not have much interfere of anonymous and active file pages. And the inactive file pages and MADV_FREE pages will be reclaimed according to their age, so we don't reclaim too many MADV_FREE pages too. Putting the MADV_FREE pages into LRU_INACTIVE_FILE_LIST also means we can reclaim the pages without swap support. This idea is suggested by Johannes. This patch doesn't move MADV_FREE pages to LRU_INACTIVE_FILE list yet to avoid bisect failure, next patch will do it. The patch is based on Minchan's original patch. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/2f87063c1e9354677b7618c647abde77b07561e5.1487965799.git.shli@fb.com Signed-off-by: Shaohua Li <shli@fb.com> Suggested-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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67afa38e01 |
mm/swap: add cache for swap slots allocation
We add per cpu caches for swap slots that can be allocated and freed quickly without the need to touch the swap info lock. Two separate caches are maintained for swap slots allocated and swap slots returned. This is to allow the swap slots to be returned to the global pool in a batch so they will have a chance to be coaelesced with other slots in a cluster. We do not reuse the slots that are returned right away, as it may increase fragmentation of the slots. The swap allocation cache is protected by a mutex as we may sleep when searching for empty slots in cache. The swap free cache is protected by a spin lock as we cannot sleep in the free path. We refill the swap slots cache when we run out of slots, and we disable the swap slots cache and drain the slots if the global number of slots fall below a low watermark threshold. We re-enable the cache agian when the slots available are above a high watermark. [ying.huang@intel.com: use raw_cpu_ptr over this_cpu_ptr for swap slots access] [tim.c.chen@linux.intel.com: add comments on locks in swap_slots.h] Link: http://lkml.kernel.org/r/20170118180327.GA24225@linux.intel.com Link: http://lkml.kernel.org/r/35de301a4eaa8daa2977de6e987f2c154385eb66.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Michal Hocko <mhocko@suse.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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7c00bafee8 |
mm/swap: free swap slots in batch
Add new functions that free unused swap slots in batches without the need to reacquire swap info lock. This improves scalability and reduce lock contention. Link: http://lkml.kernel.org/r/c25e0fcdfd237ec4ca7db91631d3b9f6ed23824e.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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36005bae20 |
mm/swap: allocate swap slots in batches
Currently, the swap slots are allocated one page at a time, causing contention to the swap_info lock protecting the swap partition on every page being swapped. This patch adds new functions get_swap_pages and scan_swap_map_slots to request multiple swap slots at once. This will reduces the lock contention on the swap_info lock. Also scan_swap_map_slots can operate more efficiently as swap slots often occurs in clusters close to each other on a swap device and it is quicker to allocate them together. Link: http://lkml.kernel.org/r/9fec2845544371f62c3763d43510045e33d286a6.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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e8c26ab605 |
mm/swap: skip readahead for unreferenced swap slots
We can avoid needlessly allocating page for swap slots that are not used by anyone. No pages have to be read in for these slots. Link: http://lkml.kernel.org/r/0784b3f20b9bd3aa5552219624cb78dc4ae710c9.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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4b3ef9daa4 |
mm/swap: split swap cache into 64MB trunks
The patch is to improve the scalability of the swap out/in via using fine grained locks for the swap cache. In current kernel, one address space will be used for each swap device. And in the common configuration, the number of the swap device is very small (one is typical). This causes the heavy lock contention on the radix tree of the address space if multiple tasks swap out/in concurrently. But in fact, there is no dependency between pages in the swap cache. So that, we can split the one shared address space for each swap device into several address spaces to reduce the lock contention. In the patch, the shared address space is split into 64MB trunks. 64MB is chosen to balance the memory space usage and effect of lock contention reduction. The size of struct address_space on x86_64 architecture is 408B, so with the patch, 6528B more memory will be used for every 1GB swap space on x86_64 architecture. One address space is still shared for the swap entries in the same 64M trunks. To avoid lock contention for the first round of swap space allocation, the order of the swap clusters in the initial free clusters list is changed. The swap space distance between the consecutive swap clusters in the free cluster list is at least 64M. After the first round of allocation, the swap clusters are expected to be freed randomly, so the lock contention should be reduced effectively. Link: http://lkml.kernel.org/r/735bab895e64c930581ffb0a05b661e01da82bc5.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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235b621767 |
mm/swap: add cluster lock
This patch is to reduce the lock contention of swap_info_struct->lock via using a more fine grained lock in swap_cluster_info for some swap operations. swap_info_struct->lock is heavily contended if multiple processes reclaim pages simultaneously. Because there is only one lock for each swap device. While in common configuration, there is only one or several swap devices in the system. The lock protects almost all swap related operations. In fact, many swap operations only access one element of swap_info_struct->swap_map array. And there is no dependency between different elements of swap_info_struct->swap_map. So a fine grained lock can be used to allow parallel access to the different elements of swap_info_struct->swap_map. In this patch, a spinlock is added to swap_cluster_info to protect the elements of swap_info_struct->swap_map in the swap cluster and the fields of swap_cluster_info. This reduced locking contention for swap_info_struct->swap_map access greatly. Because of the added spinlock, the size of swap_cluster_info increases from 4 bytes to 8 bytes on the 64 bit and 32 bit system. This will use additional 4k RAM for every 1G swap space. Because the size of swap_cluster_info is much smaller than the size of the cache line (8 vs 64 on x86_64 architecture), there may be false cache line sharing between spinlocks in swap_cluster_info. To avoid the false sharing in the first round of the swap cluster allocation, the order of the swap clusters in the free clusters list is changed. So that, the swap_cluster_info sharing the same cache line will be placed as far as possible. After the first round of allocation, the order of the clusters in free clusters list is expected to be random. So the false sharing should be not serious. Compared with a previous implementation using bit_spin_lock, the sequential swap out throughput improved about 3.2%. Test was done on a Xeon E5 v3 system. The swap device used is a RAM simulated PMEM (persistent memory) device. To test the sequential swapping out, the test case created 32 processes, which sequentially allocate and write to the anonymous pages until the RAM and part of the swap device is used. [ying.huang@intel.com: v5] Link: http://lkml.kernel.org/r/878tqeuuic.fsf_-_@yhuang-dev.intel.com [minchan@kernel.org: initialize spinlock for swap_cluster_info] Link: http://lkml.kernel.org/r/1486434945-29753-1-git-send-email-minchan@kernel.org [hughd@google.com: annotate nested locking for cluster lock] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1702161050540.21773@eggly.anvils Link: http://lkml.kernel.org/r/dbb860bbd825b1aaba18988015e8963f263c3f0d.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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f05714293a |
mm: support anonymous stable page
During developemnt for zram-swap asynchronous writeback, I found strange
corruption of compressed page, resulting in:
Modules linked in: zram(E)
CPU: 3 PID: 1520 Comm: zramd-1 Tainted: G E 4.8.0-mm1-00320-ge0d4894c9c38-dirty #3274
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
task: ffff88007620b840 task.stack: ffff880078090000
RIP: set_freeobj.part.43+0x1c/0x1f
RSP: 0018:ffff880078093ca8 EFLAGS: 00010246
RAX: 0000000000000018 RBX: ffff880076798d88 RCX: ffffffff81c408c8
RDX: 0000000000000018 RSI: 0000000000000000 RDI: 0000000000000246
RBP: ffff880078093cb0 R08: 0000000000000000 R09: 0000000000000000
R10: ffff88005bc43030 R11: 0000000000001df3 R12: ffff880076798d88
R13: 000000000005bc43 R14: ffff88007819d1b8 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff88007e380000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc934048f20 CR3: 0000000077b01000 CR4: 00000000000406e0
Call Trace:
obj_malloc+0x22b/0x260
zs_malloc+0x1e4/0x580
zram_bvec_rw+0x4cd/0x830 [zram]
page_requests_rw+0x9c/0x130 [zram]
zram_thread+0xe6/0x173 [zram]
kthread+0xca/0xe0
ret_from_fork+0x25/0x30
With investigation, it reveals currently stable page doesn't support
anonymous page. IOW, reuse_swap_page can reuse the page without waiting
writeback completion so it can overwrite page zram is compressing.
Unfortunately, zram has used per-cpu stream feature from v4.7.
It aims for increasing cache hit ratio of scratch buffer for
compressing. Downside of that approach is that zram should ask
memory space for compressed page in per-cpu context which requires
stricted gfp flag which could be failed. If so, it retries to
allocate memory space out of per-cpu context so it could get memory
this time and compress the data again, copies it to the memory space.
In this scenario, zram assumes the data should never be changed
but it is not true unless stable page supports. So, If the data is
changed under us, zram can make buffer overrun because second
compression size could be bigger than one we got in previous trial
and blindly, copy bigger size object to smaller buffer which is
buffer overrun. The overrun breaks zsmalloc free object chaining
so system goes crash like above.
I think below is same problem.
https://bugzilla.suse.com/show_bug.cgi?id=997574
Unfortunately, reuse_swap_page should be atomic so that we cannot wait on
writeback in there so the approach in this patch is simply return false if
we found it needs stable page. Although it increases memory footprint
temporarily, it happens rarely and it should be reclaimed easily althoug
it happened. Also, It would be better than waiting of IO completion,
which is critial path for application latency.
Fixes:
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36869cb93d |
Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block
Pull block layer updates from Jens Axboe: "This is the main block pull request this series. Contrary to previous release, I've kept the core and driver changes in the same branch. We always ended up having dependencies between the two for obvious reasons, so makes more sense to keep them together. That said, I'll probably try and keep more topical branches going forward, especially for cycles that end up being as busy as this one. The major parts of this pull request is: - Improved support for O_DIRECT on block devices, with a small private implementation instead of using the pig that is fs/direct-io.c. From Christoph. - Request completion tracking in a scalable fashion. This is utilized by two components in this pull, the new hybrid polling and the writeback queue throttling code. - Improved support for polling with O_DIRECT, adding a hybrid mode that combines pure polling with an initial sleep. From me. - Support for automatic throttling of writeback queues on the block side. This uses feedback from the device completion latencies to scale the queue on the block side up or down. From me. - Support from SMR drives in the block layer and for SD. From Hannes and Shaun. - Multi-connection support for nbd. From Josef. - Cleanup of request and bio flags, so we have a clear split between which are bio (or rq) private, and which ones are shared. From Christoph. - A set of patches from Bart, that improve how we handle queue stopping and starting in blk-mq. - Support for WRITE_ZEROES from Chaitanya. - Lightnvm updates from Javier/Matias. - Supoort for FC for the nvme-over-fabrics code. From James Smart. - A bunch of fixes from a whole slew of people, too many to name here" * 'for-4.10/block' of git://git.kernel.dk/linux-block: (182 commits) blk-stat: fix a few cases of missing batch flushing blk-flush: run the queue when inserting blk-mq flush elevator: make the rqhash helpers exported blk-mq: abstract out blk_mq_dispatch_rq_list() helper blk-mq: add blk_mq_start_stopped_hw_queue() block: improve handling of the magic discard payload blk-wbt: don't throttle discard or write zeroes nbd: use dev_err_ratelimited in io path nbd: reset the setup task for NBD_CLEAR_SOCK nvme-fabrics: Add FC LLDD loopback driver to test FC-NVME nvme-fabrics: Add target support for FC transport nvme-fabrics: Add host support for FC transport nvme-fabrics: Add FC transport LLDD api definitions nvme-fabrics: Add FC transport FC-NVME definitions nvme-fabrics: Add FC transport error codes to nvme.h Add type 0x28 NVME type code to scsi fc headers nvme-fabrics: patch target code in prep for FC transport support nvme-fabrics: set sqe.command_id in core not transports parser: add u64 number parser nvme-rdma: align to generic ib_event logging helper ... |
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14b468791f |
mm: workingset: move shadow entry tracking to radix tree exceptional tracking
Currently, we track the shadow entries in the page cache in the upper
bits of the radix_tree_node->count, behind the back of the radix tree
implementation. Because the radix tree code has no awareness of them,
we rely on random subtleties throughout the implementation (such as the
node->count != 1 check in the shrinking code, which is meant to exclude
multi-entry nodes but also happens to skip nodes with only one shadow
entry, as that's accounted in the upper bits). This is error prone and
has, in fact, caused the bug fixed in
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be297968da |
mm: only include blk_types in swap.h if CONFIG_SWAP is enabled
It's only needed for the CONFIG_SWAP-only use of bio_end_io_t. Because CONFIG_SWAP implies CONFIG_BLOCK this will allow to drop some ifdefs in blk_types.h. Instead we'll need to add a few explicit includes that were implicit before, though. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com> |
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2f8b544477 |
block,fs: untangle fs.h and blk_types.h
Nothing in fs.h should require blk_types.h to be included. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com> |
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6b53491598 |
mm, swap: add swap_cluster_list
This is a code clean up patch without functionality changes. The swap_cluster_list data structure and its operations are introduced to provide some better encapsulation for the free cluster and discard cluster list operations. This avoid some code duplication, improved the code readability, and reduced the total line number. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1472067356-16004-1-git-send-email-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Rik van Riel <riel@redhat.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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21f54ddae4 |
Using BUG_ON() as an assert() is _never_ acceptable
That just generally kills the machine, and makes debugging only much
harder, since the traces may long be gone.
Debugging by assert() is a disease. Don't do it. If you can continue,
you're much better off doing so with a live machine where you have a
much higher chance that the report actually makes it to the system logs,
rather than result in a machine that is just completely dead.
The only valid situation for BUG_ON() is when continuing is not an
option, because there is massive corruption. But if you are just
verifying that something is true, you warn about your broken assumptions
(preferably just once), and limp on.
Fixes:
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22f2ac51b6 |
mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()
Antonio reports the following crash when using fuse under memory pressure:
kernel BUG at /build/linux-a2WvEb/linux-4.4.0/mm/workingset.c:346!
invalid opcode: 0000 [#1] SMP
Modules linked in: all of them
CPU: 2 PID: 63 Comm: kswapd0 Not tainted 4.4.0-36-generic #55-Ubuntu
Hardware name: System manufacturer System Product Name/P8H67-M PRO, BIOS 3904 04/27/2013
task: ffff88040cae6040 ti: ffff880407488000 task.ti: ffff880407488000
RIP: shadow_lru_isolate+0x181/0x190
Call Trace:
__list_lru_walk_one.isra.3+0x8f/0x130
list_lru_walk_one+0x23/0x30
scan_shadow_nodes+0x34/0x50
shrink_slab.part.40+0x1ed/0x3d0
shrink_zone+0x2ca/0x2e0
kswapd+0x51e/0x990
kthread+0xd8/0xf0
ret_from_fork+0x3f/0x70
which corresponds to the following sanity check in the shadow node
tracking:
BUG_ON(node->count & RADIX_TREE_COUNT_MASK);
The workingset code tracks radix tree nodes that exclusively contain
shadow entries of evicted pages in them, and this (somewhat obscure)
line checks whether there are real pages left that would interfere with
reclaim of the radix tree node under memory pressure.
While discussing ways how fuse might sneak pages into the radix tree
past the workingset code, Miklos pointed to replace_page_cache_page(),
and indeed there is a problem there: it properly accounts for the old
page being removed - __delete_from_page_cache() does that - but then
does a raw raw radix_tree_insert(), not accounting for the replacement
page. Eventually the page count bits in node->count underflow while
leaving the node incorrectly linked to the shadow node LRU.
To address this, make sure replace_page_cache_page() uses the tracked
page insertion code, page_cache_tree_insert(). This fixes the page
accounting and makes sure page-containing nodes are properly unlinked
from the shadow node LRU again.
Also, make the sanity checks a bit less obscure by using the helpers for
checking the number of pages and shadows in a radix tree node.
Fixes:
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5a1c84b404 |
mm: remove reclaim and compaction retry approximations
If per-zone LRU accounting is available then there is no point approximating whether reclaim and compaction should retry based on pgdat statistics. This is effectively a revert of "mm, vmstat: remove zone and node double accounting by approximating retries" with the difference that inactive/active stats are still available. This preserves the history of why the approximation was retried and why it had to be reverted to handle OOM kills on 32-bit systems. Link: http://lkml.kernel.org/r/1469110261-7365-4-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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bca6759258 |
mm, vmstat: remove zone and node double accounting by approximating retries
The number of LRU pages, dirty pages and writeback pages must be
accounted for on both zones and nodes because of the reclaim retry
logic, compaction retry logic and highmem calculations all depending on
per-zone stats.
Many lowmem allocations are immune from OOM kill due to a check in
__alloc_pages_may_oom for (ac->high_zoneidx < ZONE_NORMAL) since commit
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a5f5f91da6 |
mm: convert zone_reclaim to node_reclaim
As reclaim is now per-node based, convert zone_reclaim to be node_reclaim. It is possible that a node will be reclaimed multiple times if it has multiple zones but this is unavoidable without caching all nodes traversed so far. The documentation and interface to userspace is the same from a configuration perspective and will will be similar in behaviour unless the node-local allocation requests were also limited to lower zones. Link: http://lkml.kernel.org/r/1467970510-21195-24-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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ef8f232799 |
mm, memcg: move memcg limit enforcement from zones to nodes
Memcg needs adjustment after moving LRUs to the node. Limits are tracked per memcg but the soft-limit excess is tracked per zone. As global page reclaim is based on the node, it is easy to imagine a situation where a zone soft limit is exceeded even though the memcg limit is fine. This patch moves the soft limit tree the node. Technically, all the variable names should also change but people are already familiar by the meaning of "mz" even if "mn" would be a more appropriate name now. Link: http://lkml.kernel.org/r/1467970510-21195-15-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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a9dd0a8310 |
mm, vmscan: make shrink_node decisions more node-centric
Earlier patches focused on having direct reclaim and kswapd use data that is node-centric for reclaiming but shrink_node() itself still uses too much zone information. This patch removes unnecessary zone-based information with the most important decision being whether to continue reclaim or not. Some memcg APIs are adjusted as a result even though memcg itself still uses some zone information. [mgorman@techsingularity.net: optimization] Link: http://lkml.kernel.org/r/1468588165-12461-2-git-send-email-mgorman@techsingularity.net Link: http://lkml.kernel.org/r/1467970510-21195-14-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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31483b6ad2 |
mm, vmscan: remove balance gap
The balance gap was introduced to apply equal pressure to all zones when reclaiming for a higher zone. With node-based LRU, the need for the balance gap is removed and the code is dead so remove it. [vbabka@suse.cz: Also remove KSWAPD_ZONE_BALANCE_GAP_RATIO] Link: http://lkml.kernel.org/r/1467970510-21195-9-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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599d0c954f |
mm, vmscan: move LRU lists to node
This moves the LRU lists from the zone to the node and related data such as counters, tracing, congestion tracking and writeback tracking. Unfortunately, due to reclaim and compaction retry logic, it is necessary to account for the number of LRU pages on both zone and node logic. Most reclaim logic is based on the node counters but the retry logic uses the zone counters which do not distinguish inactive and active sizes. It would be possible to leave the LRU counters on a per-zone basis but it's a heavier calculation across multiple cache lines that is much more frequent than the retry checks. Other than the LRU counters, this is mostly a mechanical patch but note that it introduces a number of anomalies. For example, the scans are per-zone but using per-node counters. We also mark a node as congested when a zone is congested. This causes weird problems that are fixed later but is easier to review. In the event that there is excessive overhead on 32-bit systems due to the nodes being on LRU then there are two potential solutions 1. Long-term isolation of highmem pages when reclaim is lowmem When pages are skipped, they are immediately added back onto the LRU list. If lowmem reclaim persisted for long periods of time, the same highmem pages get continually scanned. The idea would be that lowmem keeps those pages on a separate list until a reclaim for highmem pages arrives that splices the highmem pages back onto the LRU. It potentially could be implemented similar to the UNEVICTABLE list. That would reduce the skip rate with the potential corner case is that highmem pages have to be scanned and reclaimed to free lowmem slab pages. 2. Linear scan lowmem pages if the initial LRU shrink fails This will break LRU ordering but may be preferable and faster during memory pressure than skipping LRU pages. Link: http://lkml.kernel.org/r/1467970510-21195-4-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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0a0337e0d1 |
mm, oom: rework oom detection
__alloc_pages_slowpath has traditionally relied on the direct reclaim and did_some_progress as an indicator that it makes sense to retry allocation rather than declaring OOM. shrink_zones had to rely on zone_reclaimable if shrink_zone didn't make any progress to prevent from a premature OOM killer invocation - the LRU might be full of dirty or writeback pages and direct reclaim cannot clean those up. zone_reclaimable allows to rescan the reclaimable lists several times and restart if a page is freed. This is really subtle behavior and it might lead to a livelock when a single freed page keeps allocator looping but the current task will not be able to allocate that single page. OOM killer would be more appropriate than looping without any progress for unbounded amount of time. This patch changes OOM detection logic and pulls it out from shrink_zone which is too low to be appropriate for any high level decisions such as OOM which is per zonelist property. It is __alloc_pages_slowpath which knows how many attempts have been done and what was the progress so far therefore it is more appropriate to implement this logic. The new heuristic is implemented in should_reclaim_retry helper called from __alloc_pages_slowpath. It tries to be more deterministic and easier to follow. It builds on an assumption that retrying makes sense only if the currently reclaimable memory + free pages would allow the current allocation request to succeed (as per __zone_watermark_ok) at least for one zone in the usable zonelist. This alone wouldn't be sufficient, though, because the writeback might get stuck and reclaimable pages might be pinned for a really long time or even depend on the current allocation context. Therefore there is a backoff mechanism implemented which reduces the reclaim target after each reclaim round without any progress. This means that we should eventually converge to only NR_FREE_PAGES as the target and fail on the wmark check and proceed to OOM. The backoff is simple and linear with 1/16 of the reclaimable pages for each round without any progress. We are optimistic and reset counter for successful reclaim rounds. Costly high order pages mostly preserve their semantic and those without __GFP_REPEAT fail right away while those which have the flag set will back off after the amount of reclaimable pages reaches equivalent of the requested order. The only difference is that if there was no progress during the reclaim we rely on zone watermark check. This is more logical thing to do than previous 1<<order attempts which were a result of zone_reclaimable faking the progress. [vdavydov@virtuozzo.com: check classzone_idx for shrink_zone] [hannes@cmpxchg.org: separate the heuristic into should_reclaim_retry] [rientjes@google.com: use zone_page_state_snapshot for NR_FREE_PAGES] [rientjes@google.com: shrink_zones doesn't need to return anything] Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <js1304@gmail.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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6d0a07edd1 |
mm: thp: calculate the mapcount correctly for THP pages during WP faults
This will provide fully accuracy to the mapcount calculation in the
write protect faults, so page pinning will not get broken by false
positive copy-on-writes.
total_mapcount() isn't the right calculation needed in
reuse_swap_page(), so this introduces a page_trans_huge_mapcount()
that is effectively the full accurate return value for page_mapcount()
if dealing with Transparent Hugepages, however we only use the
page_trans_huge_mapcount() during COW faults where it strictly needed,
due to its higher runtime cost.
This also provide at practical zero cost the total_mapcount
information which is needed to know if we can still relocate the page
anon_vma to the local vma. If page_trans_huge_mapcount() returns 1 we
can reuse the page no matter if it's a pte or a pmd_trans_huge
triggering the fault, but we can only relocate the page anon_vma to
the local vma->anon_vma if we're sure it's only this "vma" mapping the
whole THP physical range.
Kirill A. Shutemov discovered the problem with moving the page
anon_vma to the local vma->anon_vma in a previous version of this
patch and another problem in the way page_move_anon_rmap() was called.
Andrew Morton discovered that CONFIG_SWAP=n wouldn't build in a
previous version, because reuse_swap_page must be a macro to call
page_trans_huge_mapcount from swap.h, so this uses a macro again
instead of an inline function. With this change at least it's a less
dangerous usage than it was before, because "page" is used only once
now, while with the previous code reuse_swap_page(page++) would have
called page_mapcount on page+1 and it would have increased page twice
instead of just once.
Dean Luick noticed an uninitialized variable that could result in a
rmap inefficiency for the non-THP case in a previous version.
Mike Marciniszyn said:
: Our RDMA tests are seeing an issue with memory locking that bisects to
: commit
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