Commit dbbee9d5cd ("mm/page_alloc: convert per-cpu list protection to
local_lock") folded in a workaround patch for pahole that was unable to
deal with zero-sized percpu structures.
A superior workaround is achieved with commit a0b8200d06 ("kbuild:
skip per-CPU BTF generation for pahole v1.18-v1.21").
This patch reverts the dummy field and the pahole version check.
Fixes: dbbee9d5cd ("mm/page_alloc: convert per-cpu list protection to local_lock")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge more updates from Andrew Morton:
"190 patches.
Subsystems affected by this patch series: mm (hugetlb, userfaultfd,
vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock,
migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap,
zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc,
core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs,
signals, exec, kcov, selftests, compress/decompress, and ipc"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits)
ipc/util.c: use binary search for max_idx
ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock
ipc: use kmalloc for msg_queue and shmid_kernel
ipc sem: use kvmalloc for sem_undo allocation
lib/decompressors: remove set but not used variabled 'level'
selftests/vm/pkeys: exercise x86 XSAVE init state
selftests/vm/pkeys: refill shadow register after implicit kernel write
selftests/vm/pkeys: handle negative sys_pkey_alloc() return code
selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random
kcov: add __no_sanitize_coverage to fix noinstr for all architectures
exec: remove checks in __register_bimfmt()
x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
hfsplus: report create_date to kstat.btime
hfsplus: remove unnecessary oom message
nilfs2: remove redundant continue statement in a while-loop
kprobes: remove duplicated strong free_insn_page in x86 and s390
init: print out unknown kernel parameters
checkpatch: do not complain about positive return values starting with EPOLL
checkpatch: improve the indented label test
checkpatch: scripts/spdxcheck.py now requires python3
...
make W=1 generates the following warning for mm/page_alloc.c
mm/page_alloc.c:3651:15: warning: no previous prototype for `should_fail_alloc_page' [-Wmissing-prototypes]
noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
^~~~~~~~~~~~~~~~~~~~~~
This function is deliberately split out for BPF to allow errors to be
injected. The function is not used anywhere else so it is local to the
file. Make it static which should still allow error injection to be used
similar to how block/blk-core.c:should_fail_bio() works.
Link: https://lkml.kernel.org/r/20210520084809.8576-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix some spelling mistakes in comments:
each having differents usage ==> each has a different usage
statments ==> statements
adresses ==> addresses
aggresive ==> aggressive
datas ==> data
posion ==> poison
higer ==> higher
precisly ==> precisely
wont ==> won't
We moves tha ==> We move the
endianess ==> endianness
Link: https://lkml.kernel.org/r/20210519065853.7723-2-thunder.leizhen@huawei.com
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In [1], Jann Horn points out a possible race between
prep_compound_gigantic_page and __page_cache_add_speculative. The root
cause of the possible race is prep_compound_gigantic_page uncondittionally
setting the ref count of pages to zero. It does this because
prep_compound_gigantic_page is handed a 'group' of pages from an allocator
and needs to convert that group of pages to a compound page. The ref
count of each page in this 'group' is one as set by the allocator.
However, the ref count of compound page tail pages must be zero.
The potential race comes about when ref counted pages are returned from
the allocator. When this happens, other mm code could also take a
reference on the page. __page_cache_add_speculative is one such example.
Therefore, prep_compound_gigantic_page can not just set the ref count of
pages to zero as it does today. Doing so would lose the reference taken
by any other code. This would lead to BUGs in code checking ref counts
and could possibly even lead to memory corruption.
There are two possible ways to address this issue.
1) Make all allocators of gigantic groups of pages be able to return a
properly constructed compound page.
2) Make prep_compound_gigantic_page be more careful when constructing a
compound page.
This patch takes approach 2.
In prep_compound_gigantic_page, use cmpxchg to only set ref count to zero
if it is one. If the cmpxchg fails, call synchronize_rcu() in the hope
that the extra ref count will be driopped during a rcu grace period. This
is not a performance critical code path and the wait should be
accceptable. If the ref count is still inflated after the grace period,
then undo any modifications made and return an error.
Currently prep_compound_gigantic_page is type void and does not return
errors. Modify the two callers to check for and handle error returns. On
error, the caller must free the 'group' of pages as they can not be used
to form a gigantic page. After freeing pages, the runtime caller
(alloc_fresh_huge_page) will retry the allocation once. Boot time
allocations can not be retried.
The routine prep_compound_page also unconditionally sets the ref count of
compound page tail pages to zero. However, in this case the buddy
allocator is constructing a compound page from freshly allocated pages.
The ref count on those freshly allocated pages is already zero, so the
set_page_count(p, 0) is unnecessary and could lead to confusion. Just
remove it.
[1] https://lore.kernel.org/linux-mm/CAG48ez23q0Jy9cuVnwAe7t_fdhMk2S7N5Hdi-GLcCeq5bsfLxw@mail.gmail.com/
Link: https://lkml.kernel.org/r/20210622021423.154662-3-mike.kravetz@oracle.com
Fixes: 58a84aa927 ("thp: set compound tail page _count to zero")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Jann Horn <jannh@google.com>
Cc: Youquan Song <youquan.song@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge misc updates from Andrew Morton:
"191 patches.
Subsystems affected by this patch series: kthread, ia64, scripts,
ntfs, squashfs, ocfs2, kernel/watchdog, and mm (gup, pagealloc, slab,
slub, kmemleak, dax, debug, pagecache, gup, swap, memcg, pagemap,
mprotect, bootmem, dma, tracing, vmalloc, kasan, initialization,
pagealloc, and memory-failure)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (191 commits)
mm,hwpoison: make get_hwpoison_page() call get_any_page()
mm,hwpoison: send SIGBUS with error virutal address
mm/page_alloc: split pcp->high across all online CPUs for cpuless nodes
mm/page_alloc: allow high-order pages to be stored on the per-cpu lists
mm: replace CONFIG_FLAT_NODE_MEM_MAP with CONFIG_FLATMEM
mm: replace CONFIG_NEED_MULTIPLE_NODES with CONFIG_NUMA
docs: remove description of DISCONTIGMEM
arch, mm: remove stale mentions of DISCONIGMEM
mm: remove CONFIG_DISCONTIGMEM
m68k: remove support for DISCONTIGMEM
arc: remove support for DISCONTIGMEM
arc: update comment about HIGHMEM implementation
alpha: remove DISCONTIGMEM and NUMA
mm/page_alloc: move free_the_page
mm/page_alloc: fix counting of managed_pages
mm/page_alloc: improve memmap_pages dbg msg
mm: drop SECTION_SHIFT in code comments
mm/page_alloc: introduce vm.percpu_pagelist_high_fraction
mm/page_alloc: limit the number of pages on PCP lists when reclaim is active
mm/page_alloc: scale the number of pages that are batch freed
...
Dave Hansen reported the following about Feng Tang's tests on a machine
with persistent memory onlined as a DRAM-like device.
Feng Tang tossed these on a "Cascade Lake" system with 96 threads and
~512G of persistent memory and 128G of DRAM. The PMEM is in "volatile
use" mode and being managed via the buddy just like the normal RAM.
The PMEM zones are big ones:
present 65011712 = 248 G
high 134595 = 525 M
The PMEM nodes, of course, don't have any CPUs in them.
With your series, the pcp->high value per-cpu is 69584 pages or about
270MB per CPU. Scaled up by the 96 CPU threads, that's ~26GB of
worst-case memory in the pcps per zone, or roughly 10% of the size of
the zone.
This should not cause a problem as such although it could trigger reclaim
due to pages being stored on per-cpu lists for CPUs remote to a node. It
is not possible to treat cpuless nodes exactly the same as normal nodes
but the worst-case scenario can be mitigated by splitting pcp->high across
all online CPUs for cpuless memory nodes.
Link: https://lkml.kernel.org/r/20210616110743.GK30378@techsingularity.net
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Tang, Feng" <feng.tang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The per-cpu page allocator (PCP) only stores order-0 pages. This means
that all THP and "cheap" high-order allocations including SLUB contends on
the zone->lock. This patch extends the PCP allocator to store THP and
"cheap" high-order pages. Note that struct per_cpu_pages increases in
size to 256 bytes (4 cache lines) on x86-64.
Note that this is not necessarily a universal performance win because of
how it is implemented. High-order pages can cause pcp->high to be
exceeded prematurely for lower-orders so for example, a large number of
THP pages being freed could release order-0 pages from the PCP lists.
Hence, much depends on the allocation/free pattern as observed by a single
CPU to determine if caching helps or hurts a particular workload.
That said, basic performance testing passed. The following is a netperf
UDP_STREAM test which hits the relevant patches as some of the network
allocations are high-order.
netperf-udp
5.13.0-rc2 5.13.0-rc2
mm-pcpburst-v3r4 mm-pcphighorder-v1r7
Hmean send-64 261.46 ( 0.00%) 266.30 * 1.85%*
Hmean send-128 516.35 ( 0.00%) 536.78 * 3.96%*
Hmean send-256 1014.13 ( 0.00%) 1034.63 * 2.02%*
Hmean send-1024 3907.65 ( 0.00%) 4046.11 * 3.54%*
Hmean send-2048 7492.93 ( 0.00%) 7754.85 * 3.50%*
Hmean send-3312 11410.04 ( 0.00%) 11772.32 * 3.18%*
Hmean send-4096 13521.95 ( 0.00%) 13912.34 * 2.89%*
Hmean send-8192 21660.50 ( 0.00%) 22730.72 * 4.94%*
Hmean send-16384 31902.32 ( 0.00%) 32637.50 * 2.30%*
Functionally, a patch like this is necessary to make bulk allocation of
high-order pages work with similar performance to order-0 bulk
allocations. The bulk allocator is not updated in this series as it would
have to be determined by bulk allocation users how they want to track the
order of pages allocated with the bulk allocator.
Link: https://lkml.kernel.org/r/20210611135753.GC30378@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After removal of the DISCONTIGMEM memory model the FLAT_NODE_MEM_MAP
configuration option is equivalent to FLATMEM.
Drop CONFIG_FLAT_NODE_MEM_MAP and use CONFIG_FLATMEM instead.
Link: https://lkml.kernel.org/r/20210608091316.3622-10-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After removal of DISCINTIGMEM the NEED_MULTIPLE_NODES and NUMA
configuration options are equivalent.
Drop CONFIG_NEED_MULTIPLE_NODES and use CONFIG_NUMA instead.
Done with
$ sed -i 's/CONFIG_NEED_MULTIPLE_NODES/CONFIG_NUMA/' \
$(git grep -wl CONFIG_NEED_MULTIPLE_NODES)
$ sed -i 's/NEED_MULTIPLE_NODES/NUMA/' \
$(git grep -wl NEED_MULTIPLE_NODES)
with manual tweaks afterwards.
[rppt@linux.ibm.com: fix arm boot crash]
Link: https://lkml.kernel.org/r/YMj9vHhHOiCVN4BF@linux.ibm.com
Link: https://lkml.kernel.org/r/20210608091316.3622-9-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are no architectures that support DISCONTIGMEM left.
Remove the configuration option and the dead code it was guarding in the
generic memory management code.
Link: https://lkml.kernel.org/r/20210608091316.3622-6-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Allow high order pages to be stored on PCP", v2.
The per-cpu page allocator (PCP) only handles order-0 pages. With the
series "Use local_lock for pcp protection and reduce stat overhead" and
"Calculate pcp->high based on zone sizes and active CPUs", it's now
feasible to store high-order pages on PCP lists.
This small series allows PCP to store "cheap" orders where cheap is
determined by PAGE_ALLOC_COSTLY_ORDER and THP-sized allocations.
This patch (of 2):
In the next page, free_compount_page is going to use the common helper
free_the_page. This patch moves the definition to ease review. No
functional change.
Link: https://lkml.kernel.org/r/20210603142220.10851-1-mgorman@techsingularity.net
Link: https://lkml.kernel.org/r/20210603142220.10851-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit f63661566f ("mm/page_alloc.c: clear out zone->lowmem_reserve[] if
the zone is empty") clears out zone->lowmem_reserve[] if zone is empty.
But when zone is not empty and sysctl_lowmem_reserve_ratio[i] is set to
zero, zone_managed_pages(zone) is not counted in the managed_pages either.
This is inconsistent with the description of lowmem_reserve, so fix it.
Link: https://lkml.kernel.org/r/20210527125707.3760259-1-liushixin2@huawei.com
Fixes: f63661566f ("mm/page_alloc.c: clear out zone->lowmem_reserve[] if the zone is empty")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reported-by: yangerkun <yangerkun@huawei.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This introduces a new sysctl vm.percpu_pagelist_high_fraction. It is
similar to the old vm.percpu_pagelist_fraction. The old sysctl increased
both pcp->batch and pcp->high with the higher pcp->high potentially
reducing zone->lock contention. However, the higher pcp->batch value also
potentially increased allocation latency while the PCP was refilled. This
sysctl only adjusts pcp->high so that zone->lock contention is potentially
reduced but allocation latency during a PCP refill remains the same.
# grep -E "high:|batch" /proc/zoneinfo | tail -2
high: 649
batch: 63
# sysctl vm.percpu_pagelist_high_fraction=8
# grep -E "high:|batch" /proc/zoneinfo | tail -2
high: 35071
batch: 63
# sysctl vm.percpu_pagelist_high_fraction=64
high: 4383
batch: 63
# sysctl vm.percpu_pagelist_high_fraction=0
high: 649
batch: 63
[mgorman@techsingularity.net: fix documentation]
Link: https://lkml.kernel.org/r/20210528151010.GQ30378@techsingularity.net
Link: https://lkml.kernel.org/r/20210525080119.5455-7-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When kswapd is active then direct reclaim is potentially active. In
either case, it is possible that a zone would be balanced if pages were
not trapped on PCP lists. Instead of draining remote pages, simply limit
the size of the PCP lists while kswapd is active.
Link: https://lkml.kernel.org/r/20210525080119.5455-6-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a task is freeing a large number of order-0 pages, it may acquire the
zone->lock multiple times freeing pages in batches. This may
unnecessarily contend on the zone lock when freeing very large number of
pages. This patch adapts the size of the batch based on the recent
pattern to scale the batch size for subsequent frees.
As the machines I used were not large enough to test this are not large
enough to illustrate a problem, a debugging patch shows patterns like the
following (slightly editted for clarity)
Baseline vanilla kernel
time-unmap-14426 [...] free_pcppages_bulk: free 63 count 378 high 378
time-unmap-14426 [...] free_pcppages_bulk: free 63 count 378 high 378
time-unmap-14426 [...] free_pcppages_bulk: free 63 count 378 high 378
time-unmap-14426 [...] free_pcppages_bulk: free 63 count 378 high 378
time-unmap-14426 [...] free_pcppages_bulk: free 63 count 378 high 378
With patches
time-unmap-7724 [...] free_pcppages_bulk: free 126 count 814 high 814
time-unmap-7724 [...] free_pcppages_bulk: free 252 count 814 high 814
time-unmap-7724 [...] free_pcppages_bulk: free 504 count 814 high 814
time-unmap-7724 [...] free_pcppages_bulk: free 751 count 814 high 814
time-unmap-7724 [...] free_pcppages_bulk: free 751 count 814 high 814
Link: https://lkml.kernel.org/r/20210525080119.5455-5-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The PCP high watermark is based on the number of online CPUs so the
watermarks must be adjusted during CPU hotplug. At the time of
hot-remove, the number of online CPUs is already adjusted but during
hot-add, a delta needs to be applied to update PCP to the correct value.
After this patch is applied, the high watermarks are adjusted correctly.
# grep high: /proc/zoneinfo | tail -1
high: 649
# echo 0 > /sys/devices/system/cpu/cpu4/online
# grep high: /proc/zoneinfo | tail -1
high: 664
# echo 1 > /sys/devices/system/cpu/cpu4/online
# grep high: /proc/zoneinfo | tail -1
high: 649
Link: https://lkml.kernel.org/r/20210525080119.5455-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The pcp high watermark is based on the batch size but there is no
relationship between them other than it is convenient to use early in
boot.
This patch takes the first step and bases pcp->high on the zone low
watermark split across the number of CPUs local to a zone while the batch
size remains the same to avoid increasing allocation latencies. The
intent behind the default pcp->high is "set the number of PCP pages such
that if they are all full that background reclaim is not started
prematurely".
Note that in this patch the pcp->high values are adjusted after memory
hotplug events, min_free_kbytes adjustments and watermark scale factor
adjustments but not CPU hotplug events which is handled later in the
series.
On a test KVM instance;
Before grep -E "high:|batch" /proc/zoneinfo | tail -2
high: 378
batch: 63
After grep -E "high:|batch" /proc/zoneinfo | tail -2
high: 649
batch: 63
[mgorman@techsingularity.net: fix __setup_per_zone_wmarks for parallel memory
hotplug]
Link: https://lkml.kernel.org/r/20210528105925.GN30378@techsingularity.net
Link: https://lkml.kernel.org/r/20210525080119.5455-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Calculate pcp->high based on zone sizes and active CPUs", v2.
The per-cpu page allocator (PCP) is meant to reduce contention on the zone
lock but the sizing of batch and high is archaic and neither takes the
zone size into account or the number of CPUs local to a zone. With larger
zones and more CPUs per node, the contention is getting worse.
Furthermore, the fact that vm.percpu_pagelist_fraction adjusts both batch
and high values means that the sysctl can reduce zone lock contention but
also increase allocation latencies.
This series disassociates pcp->high from pcp->batch and then scales
pcp->high based on the size of the local zone with limited impact to
reclaim and accounting for active CPUs but leaves pcp->batch static. It
also adapts the number of pages that can be on the pcp list based on
recent freeing patterns.
The motivation is partially to adjust to larger memory sizes but is also
driven by the fact that large batches of page freeing via release_pages()
often shows zone contention as a major part of the problem. Another is a
bug report based on an older kernel where a multi-terabyte process can
takes several minutes to exit. A workaround was to use
vm.percpu_pagelist_fraction to increase the pcp->high value but testing
indicated that a production workload could not use the same values because
of an increase in allocation latencies. Unfortunately, I cannot reproduce
this test case myself as the multi-terabyte machines are in active use but
it should alleviate the problem.
The series aims to address both and partially acts as a pre-requisite.
pcp only works with order-0 which is useless for SLUB (when using high
orders) and THP (unconditionally). To store high-order pages on PCP, the
pcp->high values need to be increased first.
This patch (of 6):
The vm.percpu_pagelist_fraction is used to increase the batch and high
limits for the per-cpu page allocator (PCP). The intent behind the sysctl
is to reduce zone lock acquisition when allocating/freeing pages but it
has a problem. While it can decrease contention, it can also increase
latency on the allocation side due to unreasonably large batch sizes.
This leads to games where an administrator adjusts
percpu_pagelist_fraction on the fly to work around contention and
allocation latency problems.
This series aims to alleviate the problems with zone lock contention while
avoiding the allocation-side latency problems. For the purposes of
review, it's easier to remove this sysctl now and reintroduce a similar
sysctl later in the series that deals only with pcp->high.
Link: https://lkml.kernel.org/r/20210525080119.5455-1-mgorman@techsingularity.net
Link: https://lkml.kernel.org/r/20210525080119.5455-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
alloc_contig_dump_pages() aims for helping debugging page migration
failure by elevated page refcount compared to expected_count. (for the
detail, please look at migrate_page_move_mapping)
However, -ENOMEM is just the case that system is under memory pressure
state, not relevant with page refcount at all. Thus, the dumping page
list is not helpful for the debugging point of view.
Link: https://lkml.kernel.org/r/YKa2Wyo9xqIErpfa@google.com
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: John Dias <joaodias@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
VM events do not need explicit protection by disabling IRQs so update the
counter with IRQs enabled in __free_pages_ok.
Link: https://lkml.kernel.org/r/20210512095458.30632-10-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Historically when freeing pages, free_one_page() assumed that callers had
IRQs disabled and the zone->lock could be acquired with spin_lock(). This
confuses the scope of what local_lock_irq is protecting and what
zone->lock is protecting in free_unref_page_list in particular.
This patch uses spin_lock_irqsave() for the zone->lock in free_one_page()
instead of relying on callers to have disabled IRQs.
free_unref_page_commit() is changed to only deal with PCP pages protected
by the local lock. free_unref_page_list() then first frees isolated pages
to the buddy lists with free_one_page() and frees the rest of the pages to
the PCP via free_unref_page_commit(). The end result is that
free_one_page() is no longer depending on side-effects of local_lock to be
correct.
Note that this may incur a performance penalty while memory hot-remove is
running but that is not a common operation.
[lkp@intel.com: Ensure CMA pages get addded to correct pcp list]
Link: https://lkml.kernel.org/r/20210512095458.30632-9-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__free_pages_ok() disables IRQs before calling a common helper
free_one_page() that acquires the zone lock. This is not safe according
to Documentation/locking/locktypes.rst and in this context, IRQ disabling
is not protecting a per_cpu_pages structure either or a local_lock would
be used.
This patch explicitly acquires the lock with spin_lock_irqsave instead of
relying on a helper. This removes the last instance of local_irq_save()
in page_alloc.c.
Link: https://lkml.kernel.org/r/20210512095458.30632-8-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
IRQs are left disabled for the zone and node VM event counters. This is
unnecessary as the affected counters are allowed to race for preemmption
and IRQs.
This patch reduces the scope of IRQs being disabled via
local_[lock|unlock]_irq on !PREEMPT_RT kernels. One
__mod_zone_freepage_state is still called with IRQs disabled. While this
could be moved out, it's not free on all architectures as some require
IRQs to be disabled for mod_zone_page_state on !PREEMPT_RT kernels.
Link: https://lkml.kernel.org/r/20210512095458.30632-7-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that the zone_statistics are simple counters that do not require
special protection, the bulk allocator accounting updates can be batch
updated without adding too much complexity with protected RMW updates or
using xchg.
Link: https://lkml.kernel.org/r/20210512095458.30632-6-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
NUMA statistics are maintained on the zone level for hits, misses, foreign
etc but nothing relies on them being perfectly accurate for functional
correctness. The counters are used by userspace to get a general overview
of a workloads NUMA behaviour but the page allocator incurs a high cost to
maintain perfect accuracy similar to what is required for a vmstat like
NR_FREE_PAGES. There even is a sysctl vm.numa_stat to allow userspace to
turn off the collection of NUMA statistics like NUMA_HIT.
This patch converts NUMA_HIT and friends to be NUMA events with similar
accuracy to VM events. There is a possibility that slight errors will be
introduced but the overall trend as seen by userspace will be similar.
The counters are no longer updated from vmstat_refresh context as it is
unnecessary overhead for counters that may never be read by userspace.
Note that counters could be maintained at the node level to save space but
it would have a user-visible impact due to /proc/zoneinfo.
[lkp@intel.com: Fix misplaced closing brace for !CONFIG_NUMA]
Link: https://lkml.kernel.org/r/20210512095458.30632-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a lack of clarity of what exactly
local_irq_save/local_irq_restore protects in page_alloc.c . It conflates
the protection of per-cpu page allocation structures with per-cpu vmstat
deltas.
This patch protects the PCP structure using local_lock which for most
configurations is identical to IRQ enabling/disabling. The scope of the
lock is still wider than it should be but this is decreased later.
It is possible for the local_lock to be embedded safely within struct
per_cpu_pages but it adds complexity to free_unref_page_list.
[akpm@linux-foundation.org: coding style fixes]
[mgorman@techsingularity.net: work around a pahole limitation with zero-sized struct pagesets]
Link: https://lkml.kernel.org/r/20210526080741.GW30378@techsingularity.net
[lkp@intel.com: Make pagesets static]
Link: https://lkml.kernel.org/r/20210512095458.30632-3-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The PCP (per-cpu page allocator in page_alloc.c) shares locking
requirements with vmstat and the zone lock which is inconvenient and
causes some issues. For example, the PCP list and vmstat share the same
per-cpu space meaning that it's possible that vmstat updates dirty cache
lines holding per-cpu lists across CPUs unless padding is used. Second,
PREEMPT_RT does not want to disable IRQs for too long in the page
allocator.
This series splits the locking requirements and uses locks types more
suitable for PREEMPT_RT, reduces the time when special locking is required
for stats and reduces the time when IRQs need to be disabled on
!PREEMPT_RT kernels.
Why local_lock? PREEMPT_RT considers the following sequence to be unsafe
as documented in Documentation/locking/locktypes.rst
local_irq_disable();
spin_lock(&lock);
The pcp allocator has this sequence for rmqueue_pcplist (local_irq_save)
-> __rmqueue_pcplist -> rmqueue_bulk (spin_lock). While it's possible to
separate this out, it generally means there are points where we enable
IRQs and reenable them again immediately. To prevent a migration and the
per-cpu pointer going stale, migrate_disable is also needed. That is a
custom lock that is similar, but worse, than local_lock. Furthermore, on
PREEMPT_RT, it's undesirable to leave IRQs disabled for too long. By
converting to local_lock which disables migration on PREEMPT_RT, the
locking requirements can be separated and start moving the protections for
PCP, stats and the zone lock to PREEMPT_RT-safe equivalent locking. As a
bonus, local_lock also means that PROVE_LOCKING does something useful.
After that, it's obvious that zone_statistics incurs too much overhead and
leaves IRQs disabled for longer than necessary on !PREEMPT_RT kernels.
zone_statistics uses perfectly accurate counters requiring IRQs be
disabled for parallel RMW sequences when inaccurate ones like vm_events
would do. The series makes the NUMA statistics (NUMA_HIT and friends)
inaccurate counters that then require no special protection on
!PREEMPT_RT.
The bulk page allocator can then do stat updates in bulk with IRQs enabled
which should improve the efficiency. Technically, this could have been
done without the local_lock and vmstat conversion work and the order
simply reflects the timing of when different series were implemented.
Finally, there are places where we conflate IRQs being disabled for the
PCP with the IRQ-safe zone spinlock. The remainder of the series reduces
the scope of what is protected by disabled IRQs on !PREEMPT_RT kernels.
By the end of the series, page_alloc.c does not call local_irq_save so the
locking scope is a bit clearer. The one exception is that modifying
NR_FREE_PAGES still happens in places where it's known the IRQs are
disabled as it's harmless for PREEMPT_RT and would be expensive to split
the locking there.
No performance data is included because despite the overhead of the stats,
it's within the noise for most workloads on !PREEMPT_RT. However, Jesper
Dangaard Brouer ran a page allocation microbenchmark on a E5-1650 v4 @
3.60GHz CPU on the first version of this series. Focusing on the array
variant of the bulk page allocator reveals the following.
(CPU: Intel(R) Xeon(R) CPU E5-1650 v4 @ 3.60GHz)
ARRAY variant: time_bulk_page_alloc_free_array: step=bulk size
Baseline Patched
1 56.383 54.225 (+3.83%)
2 40.047 35.492 (+11.38%)
3 37.339 32.643 (+12.58%)
4 35.578 30.992 (+12.89%)
8 33.592 29.606 (+11.87%)
16 32.362 28.532 (+11.85%)
32 31.476 27.728 (+11.91%)
64 30.633 27.252 (+11.04%)
128 30.596 27.090 (+11.46%)
While this is a positive outcome, the series is more likely to be
interesting to the RT people in terms of getting parts of the PREEMPT_RT
tree into mainline.
This patch (of 9):
The per-cpu page allocator lists and the per-cpu vmstat deltas are stored
in the same struct per_cpu_pages even though vmstats have no direct impact
on the per-cpu page lists. This is inconsistent because the vmstats for a
node are stored on a dedicated structure. The bigger issue is that the
per_cpu_pages structure is not cache-aligned and stat updates either cache
conflict with adjacent per-cpu lists incurring a runtime cost or padding
is required incurring a memory cost.
This patch splits the per-cpu pagelists and the vmstat deltas into
separate structures. It's mostly a mechanical conversion but some
variable renaming is done to clearly distinguish the per-cpu pages
structure (pcp) from the vmstats (pzstats).
Superficially, this appears to increase the size of the per_cpu_pages
structure but the movement of expire fills a structure hole so there is no
impact overall.
[mgorman@techsingularity.net: make it W=1 cleaner]
Link: https://lkml.kernel.org/r/20210514144622.GA3735@techsingularity.net
[mgorman@techsingularity.net: make it W=1 even cleaner]
Link: https://lkml.kernel.org/r/20210516140705.GB3735@techsingularity.net
[lkp@intel.com: check struct per_cpu_zonestat has a non-zero size]
[vbabka@suse.cz: Init zone->per_cpu_zonestats properly]
Link: https://lkml.kernel.org/r/20210512095458.30632-1-mgorman@techsingularity.net
Link: https://lkml.kernel.org/r/20210512095458.30632-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Having such debug messages in the dmesg log may confuse users. Therefore
restrict debug output to cases where DEBUG is defined or dynamic debugging
is enabled for the respective code piece.
Link: https://lkml.kernel.org/r/976adb93-3041-ce63-48fc-55a6096a51c1@gmail.com
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The struct page is not modified by these routines, so it can be marked
const.
Link: https://lkml.kernel.org/r/20210416231531.2521383-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A customer experienced a low-memory situation and decided to issue a
SIGKILL (i.e. a fatal signal). Instead of promptly terminating as one
would expect, the aforementioned task remained unresponsive.
Further investigation indicated that the task was "stuck" in the
reclaim/compaction retry loop. Now, it does not make sense to retry
compaction when a fatal signal is pending.
In the context of try_to_compact_pages(), indeed COMPACT_SKIPPED can be
returned; albeit, not every zone, on the zone list, would be considered in
the case a fatal signal is found to be pending. Yet, in
should_compact_retry(), given the last known compaction result, each zone,
on the zone list, can be considered/or checked (see
compaction_zonelist_suitable()). For example, if a zone was found to
succeed, then reclaim/compaction would be tried again (notwithstanding the
above).
This patch ensures that compaction is not needlessly retried irrespective
of the last known compaction result e.g. if it was skipped, in the
unlikely case a fatal signal is found pending. So, OOM is at least
attempted.
Link: https://lkml.kernel.org/r/20210520142901.3371299-1-atomlin@redhat.com
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Constify struct page arguments".
While working on various solutions to the 32-bit struct page size
regression, one of the problems I found was the networking stack expects
to be able to pass const struct page pointers around, and the mm doesn't
provide a lot of const-friendly functions to call. The root tangle of
problems is that a lot of functions call VM_BUG_ON_PAGE(), which calls
dump_page(), which calls a lot of functions which don't take a const
struct page (but could be const).
This patch (of 6):
The only caller of __dump_page() now opencodes dump_page(), so remove it
as an externally visible symbol.
Link: https://lkml.kernel.org/r/20210416231531.2521383-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20210416231531.2521383-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Dave Jones reported the following
This made it into 5.13 final, and completely breaks NFSD for me
(Serving tcp v3 mounts). Existing mounts on clients hang, as do
new mounts from new clients. Rebooting the server back to rc7
everything recovers.
The commit b3b64ebd38 ("mm/page_alloc: do bulk array bounds check after
checking populated elements") returns the wrong value if the array is
already populated which is interpreted as an allocation failure. Dave
reported this fixes his problem and it also passed a test running dbench
over NFS.
Link: https://lkml.kernel.org/r/20210628150219.GC3840@techsingularity.net
Fixes: b3b64ebd38 ("mm/page_alloc: do bulk array bounds check after checking populated elements")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Tested-by: Dave Jones <davej@codemonkey.org.uk>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org> [5.13+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On systems with memory nodes sorted in descending order, for instance Dell
Precision WorkStation T5500, the struct pages for higher PFNs and
respectively lower nodes, could be overwritten by the initialization of
struct pages corresponding to the holes in the memory sections.
For example for the below memory layout
[ 0.245624] Early memory node ranges
[ 0.248496] node 1: [mem 0x0000000000001000-0x0000000000090fff]
[ 0.251376] node 1: [mem 0x0000000000100000-0x00000000dbdf8fff]
[ 0.254256] node 1: [mem 0x0000000100000000-0x0000001423ffffff]
[ 0.257144] node 0: [mem 0x0000001424000000-0x0000002023ffffff]
the range 0x1424000000 - 0x1428000000 in the beginning of node 0 starts in
the middle of a section and will be considered as a hole during the
initialization of the last section in node 1.
The wrong initialization of the memory map causes panic on boot when
CONFIG_DEBUG_VM is enabled.
Reorder loop order of the memory map initialization so that the outer loop
will always iterate over populated memory regions in the ascending order
and the inner loop will select the zone corresponding to the PFN range.
This way initialization of the struct pages for the memory holes will be
always done for the ranges that are actually not populated.
[akpm@linux-foundation.org: coding style fixes]
Link: https://lkml.kernel.org/r/YNXlMqBbL+tBG7yq@kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=213073
Link: https://lkml.kernel.org/r/20210624062305.10940-1-rppt@kernel.org
Fixes: 0740a50b9b ("mm/page_alloc.c: refactor initialization of struct page for holes in memory layout")
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Boris Petkov <bp@alien8.de>
Cc: Robert Shteynfeld <robert.shteynfeld@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Optimise SVE switching for CPUs with 128-bit implementations.
- Fix output format from SVE selftest.
- Add support for versions v1.2 and 1.3 of the SMC calling convention.
- Allow Pointer Authentication to be configured independently for
kernel and userspace.
- PMU driver cleanups for managing IRQ affinity and exposing event
attributes via sysfs.
- KASAN optimisations for both hardware tagging (MTE) and out-of-line
software tagging implementations.
- Relax frame record alignment requirements to facilitate 8-byte
alignment with KASAN and Clang.
- Cleanup of page-table definitions and removal of unused memory types.
- Reduction of ARCH_DMA_MINALIGN back to 64 bytes.
- Refactoring of our instruction decoding routines and addition of some
missing encodings.
- Move entry code moved into C and hardened against harmful compiler
instrumentation.
- Update booting requirements for the FEAT_HCX feature, added to v8.7
of the architecture.
- Fix resume from idle when pNMI is being used.
- Additional CPU sanity checks for MTE and preparatory changes for
systems where not all of the CPUs support 32-bit EL0.
- Update our kernel string routines to the latest Cortex Strings
implementation.
- Big cleanup of our cache maintenance routines, which were confusingly
named and inconsistent in their implementations.
- Tweak linker flags so that GDB can understand vmlinux when using RELR
relocations.
- Boot path cleanups to enable early initialisation of per-cpu
operations needed by KCSAN.
- Non-critical fixes and miscellaneous cleanup.
-----BEGIN PGP SIGNATURE-----
iQFEBAABCgAuFiEEPxTL6PPUbjXGY88ct6xw3ITBYzQFAmDUh1YQHHdpbGxAa2Vy
bmVsLm9yZwAKCRC3rHDchMFjNDaUCAC+2Jy2Yopd94uBPYajGybM0rqCUgE7b5n1
A7UzmQ6fia2hwqCPmxGG+sRabovwN7C1bKrUCc03RIbErIa7wum1edeyqmF/Aw44
DUDY1MAOSZaFmX8L62QCvxG1hfdLPtGmHMd1hdXvxYK7PCaigEFnzbLRWTtgE+Ok
JhdvNfsoeITJObHnvYPF3rV3NAbyYni9aNJ5AC/qb3dlf6XigEraXaMj29XHKfwc
+vmn+25oqFkLHyFeguqIoK+vUQAy/8TjFfjX83eN3LZknNhDJgWS1Iq1Nm+Vxt62
RvDUUecWJjAooCWgmil6pt0enI+q6E8LcX3A3cWWrM6psbxnYzkU
=I6KS
-----END PGP SIGNATURE-----
Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 updates from Will Deacon:
"There's a reasonable amount here and the juicy details are all below.
It's worth noting that the MTE/KASAN changes strayed outside of our
usual directories due to core mm changes and some associated changes
to some other architectures; Andrew asked for us to carry these [1]
rather that take them via the -mm tree.
Summary:
- Optimise SVE switching for CPUs with 128-bit implementations.
- Fix output format from SVE selftest.
- Add support for versions v1.2 and 1.3 of the SMC calling
convention.
- Allow Pointer Authentication to be configured independently for
kernel and userspace.
- PMU driver cleanups for managing IRQ affinity and exposing event
attributes via sysfs.
- KASAN optimisations for both hardware tagging (MTE) and out-of-line
software tagging implementations.
- Relax frame record alignment requirements to facilitate 8-byte
alignment with KASAN and Clang.
- Cleanup of page-table definitions and removal of unused memory
types.
- Reduction of ARCH_DMA_MINALIGN back to 64 bytes.
- Refactoring of our instruction decoding routines and addition of
some missing encodings.
- Move entry code moved into C and hardened against harmful compiler
instrumentation.
- Update booting requirements for the FEAT_HCX feature, added to v8.7
of the architecture.
- Fix resume from idle when pNMI is being used.
- Additional CPU sanity checks for MTE and preparatory changes for
systems where not all of the CPUs support 32-bit EL0.
- Update our kernel string routines to the latest Cortex Strings
implementation.
- Big cleanup of our cache maintenance routines, which were
confusingly named and inconsistent in their implementations.
- Tweak linker flags so that GDB can understand vmlinux when using
RELR relocations.
- Boot path cleanups to enable early initialisation of per-cpu
operations needed by KCSAN.
- Non-critical fixes and miscellaneous cleanup"
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (150 commits)
arm64: tlb: fix the TTL value of tlb_get_level
arm64: Restrict undef hook for cpufeature registers
arm64/mm: Rename ARM64_SWAPPER_USES_SECTION_MAPS
arm64: insn: avoid circular include dependency
arm64: smp: Bump debugging information print down to KERN_DEBUG
drivers/perf: fix the missed ida_simple_remove() in ddr_perf_probe()
perf/arm-cmn: Fix invalid pointer when access dtc object sharing the same IRQ number
arm64: suspend: Use cpuidle context helpers in cpu_suspend()
PSCI: Use cpuidle context helpers in psci_cpu_suspend_enter()
arm64: Convert cpu_do_idle() to using cpuidle context helpers
arm64: Add cpuidle context save/restore helpers
arm64: head: fix code comments in set_cpu_boot_mode_flag
arm64: mm: drop unused __pa(__idmap_text_start)
arm64: mm: fix the count comments in compute_indices
arm64/mm: Fix ttbr0 values stored in struct thread_info for software-pan
arm64: mm: Pass original fault address to handle_mm_fault()
arm64/mm: Drop SECTION_[SHIFT|SIZE|MASK]
arm64/mm: Use CONT_PMD_SHIFT for ARM64_MEMSTART_SHIFT
arm64/mm: Drop SWAPPER_INIT_MAP_SIZE
arm64: Conditionally configure PTR_AUTH key of the kernel.
...
Dave Jones reported the following
This made it into 5.13 final, and completely breaks NFSD for me
(Serving tcp v3 mounts). Existing mounts on clients hang, as do
new mounts from new clients. Rebooting the server back to rc7
everything recovers.
The commit b3b64ebd38 ("mm/page_alloc: do bulk array bounds check after
checking populated elements") returns the wrong value if the array is
already populated which is interpreted as an allocation failure. Dave
reported this fixes his problem and it also passed a test running dbench
over NFS.
Fixes: b3b64ebd38 ("mm/page_alloc: do bulk array bounds check after checking populated elements")
Reported-and-tested-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: <stable@vger.kernel.org> [5.13+]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Dan Carpenter reported the following
The patch 0f87d9d30f: "mm/page_alloc: add an array-based interface
to the bulk page allocator" from Apr 29, 2021, leads to the following
static checker warning:
mm/page_alloc.c:5338 __alloc_pages_bulk()
warn: potentially one past the end of array 'page_array[nr_populated]'
The problem can occur if an array is passed in that is fully populated.
That potentially ends up allocating a single page and storing it past
the end of the array. This patch returns 0 if the array is fully
populated.
Link: https://lkml.kernel.org/r/20210618125102.GU30378@techsingularity.net
Fixes: 0f87d9d30f ("mm/page_alloc: add an array-based interface to the bulk page allocator")
Signed-off-by: Mel Gorman <mgorman@techsinguliarity.net>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.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>
In the event that somebody would call this with an already fully
populated page_array, the last loop iteration would do an access beyond
the end of page_array.
It's of course extremely unlikely that would ever be done, but this
triggers my internal static analyzer. Also, if it really is not
supposed to be invoked this way (i.e., with no NULL entries in
page_array), the nr_populated<nr_pages check could simply be removed
instead.
Link: https://lkml.kernel.org/r/20210507064504.1712559-1-linux@rasmusvillemoes.dk
Fixes: 0f87d9d30f ("mm/page_alloc: add an array-based interface to the bulk page allocator")
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Recently we found that there is a lot MemFree left in /proc/meminfo
after do a lot of pages soft offline, it's not quite correct.
Before Oscar's rework of soft offline for free pages [1], if we soft
offline free pages, these pages are left in buddy with HWPoison flag,
and NR_FREE_PAGES is not updated immediately. So the difference between
NR_FREE_PAGES and real number of available free pages is also even big
at the beginning.
However, with the workload running, when we catch HWPoison page in any
alloc functions subsequently, we will remove it from buddy, meanwhile
update the NR_FREE_PAGES and try again, so the NR_FREE_PAGES will get
more and more closer to the real number of available free pages.
(regardless of unpoison_memory())
Now, for offline free pages, after a successful call
take_page_off_buddy(), the page is no longer belong to buddy allocator,
and will not be used any more, but we missed accounting NR_FREE_PAGES in
this situation, and there is no chance to be updated later.
Do update in take_page_off_buddy() like rmqueue() does, but avoid double
counting if some one already set_migratetype_isolate() on the page.
[1]: commit 06be6ff3d2 ("mm,hwpoison: rework soft offline for free pages")
Link: https://lkml.kernel.org/r/20210526075247.11130-1-dinghui@sangfor.com.cn
Fixes: 06be6ff3d2 ("mm,hwpoison: rework soft offline for free pages")
Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
Suggested-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Poisoning freed pages protects against kernel use-after-free. The
likelihood of such a bug involving kernel pages is significantly higher
than that for user pages. At the same time, poisoning freed pages can
impose a significant performance cost, which cannot always be justified
for user pages given the lower probability of finding a bug. Therefore,
disable freed user page poisoning when using HW tags. We identify
"user" pages via the flag set GFP_HIGHUSER_MOVABLE, which indicates
a strong likelihood of not being directly accessible to the kernel.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://linux-review.googlesource.com/id/I716846e2de8ef179f44e835770df7e6307be96c9
Link: https://lore.kernel.org/r/20210602235230.3928842-5-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Currently, on an anonymous page fault, the kernel allocates a zeroed
page and maps it in user space. If the mapping is tagged (PROT_MTE),
set_pte_at() additionally clears the tags. It is, however, more
efficient to clear the tags at the same time as zeroing the data on
allocation. To avoid clearing the tags on any page (which may not be
mapped as tagged), only do this if the vma flags contain VM_MTE. This
requires introducing a new GFP flag that is used to determine whether
to clear the tags.
The DC GZVA instruction with a 0 top byte (and 0 tag) requires
top-byte-ignore. Set the TCR_EL1.{TBI1,TBID1} bits irrespective of
whether KASAN_HW is enabled.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Co-developed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://linux-review.googlesource.com/id/Id46dc94e30fe11474f7e54f5d65e7658dbdddb26
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20210602235230.3928842-4-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Currently with integrated init page_alloc.c needs to know whether
kasan_alloc_pages() will zero initialize memory, but this will start
becoming more complicated once we start adding tag initialization
support for user pages. To avoid page_alloc.c needing to know more
details of what integrated init will do, move the unpoisoning logic
for integrated init into the HW tags implementation. Currently the
logic is identical but it will diverge in subsequent patches.
For symmetry do the same for poisoning although this logic will
be unaffected by subsequent patches.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://linux-review.googlesource.com/id/I2c550234c6c4a893c48c18ff0c6ce658c7c67056
Link: https://lore.kernel.org/r/20210602235230.3928842-3-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
succed -> succeed in mm/hugetlb.c
wil -> will in mm/mempolicy.c
wit -> with in mm/page_alloc.c
Retruns -> Returns in mm/page_vma_mapped.c
confict -> conflict in mm/secretmem.c
No functionality changed.
Link: https://lkml.kernel.org/r/20210408140027.60623-1-lujialin4@huawei.com
Signed-off-by: Lu Jialin <lujialin4@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zone_pcp_reset allegedly protects against a race with drain_pages using
local_irq_save but this is bogus. local_irq_save only operates on the
local CPU. If memory hotplug is running on CPU A and drain_pages is
running on CPU B, disabling IRQs on CPU A does not affect CPU B and
offers no protection.
This patch deletes IRQ disable/enable on the grounds that IRQs protect
nothing and assumes the existing hotplug paths guarantees the PCP cannot
be used after zone_pcp_enable(). That should be the case already
because all the pages have been freed and there is no page to put on the
PCP lists.
Link: https://lkml.kernel.org/r/20210412090346.GQ3697@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
PF_MEMALLOC_PIN is only honored for CMA pages, extend this flag to work
for any allocations from ZONE_MOVABLE by removing __GFP_MOVABLE from
gfp_mask when this flag is passed in the current context.
Add is_pinnable_page() to return true if page is in a pinnable page. A
pinnable page is not in ZONE_MOVABLE and not of MIGRATE_CMA type.
Link: https://lkml.kernel.org/r/20210215161349.246722-8-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.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>
Function current_gfp_context() is called after fast path. However, soon
we will add more constraints which will also limit zones based on
context. Move this call into fast path, and apply the correct
constraints for all allocations.
Also update .reclaim_idx based on value returned by
current_gfp_context() because it soon will modify the allowed zones.
Note:
With this patch we will do one extra current->flags load during fast path,
but we already load current->flags in fast-path:
__alloc_pages()
prepare_alloc_pages()
current_alloc_flags(gfp_mask, *alloc_flags);
Later, when we add the zone constrain logic to current_gfp_context() we
will be able to remove current->flags load from current_alloc_flags, and
therefore return fast-path to the current performance level.
Link: https://lkml.kernel.org/r/20210215161349.246722-7-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.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>
PF_MEMALLOC_NOCMA is used ot guarantee that the allocator will not
return pages that might belong to CMA region. This is currently used
for long term gup to make sure that such pins are not going to be done
on any CMA pages.
When PF_MEMALLOC_NOCMA has been introduced we haven't realized that it
is focusing on CMA pages too much and that there is larger class of
pages that need the same treatment. MOVABLE zone cannot contain any
long term pins as well so it makes sense to reuse and redefine this flag
for that usecase as well. Rename the flag to PF_MEMALLOC_PIN which
defines an allocation context which can only get pages suitable for
long-term pins.
Also rename: memalloc_nocma_save()/memalloc_nocma_restore to
memalloc_pin_save()/memalloc_pin_restore() and make the new functions
common.
[rppt@linux.ibm.com: fix renaming of PF_MEMALLOC_NOCMA to PF_MEMALLOC_PIN]
Link: https://lkml.kernel.org/r/20210331163816.11517-1-rppt@kernel.org
Link: https://lkml.kernel.org/r/20210215161349.246722-6-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.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>
