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![Michal Hocko](/assets/img/avatar_default.png)
compaction has been disabled for GFP_NOFS and GFP_NOIO requests since
the direct compaction was introduced by commit 56de7263fc
("mm:
compaction: direct compact when a high-order allocation fails"). The
main reason is that the migration of page cache pages might recurse back
to fs/io layer and we could potentially deadlock. This is overly
conservative because all the anonymous memory is migrateable in the
GFP_NOFS context just fine. This might be a large portion of the memory
in many/most workkloads.
Remove the GFP_NOFS restriction and make sure that we skip all fs pages
(those with a mapping) while isolating pages to be migrated. We cannot
consider clean fs pages because they might need a metadata update so
only isolate pages without any mapping for nofs requests.
The effect of this patch will be probably very limited in many/most
workloads because higher order GFP_NOFS requests are quite rare,
although different configurations might lead to very different results.
David Chinner has mentioned a heavy metadata workload with 64kB block
which to quote him:
: Unfortunately, there was an era of cargo cult configuration tweaks in the
: Ceph community that has resulted in a large number of production machines
: with XFS filesystems configured this way. And a lot of them store large
: numbers of small files and run under significant sustained memory
: pressure.
:
: I slowly working towards getting rid of these high order allocations and
: replacing them with the equivalent number of single page allocations, but
: I haven't got that (complex) change working yet.
We can do the following to simulate that workload:
$ mkfs.xfs -f -n size=64k <dev>
$ mount <dev> /mnt/scratch
$ time ./fs_mark -D 10000 -S0 -n 100000 -s 0 -L 32 \
-d /mnt/scratch/0 -d /mnt/scratch/1 \
-d /mnt/scratch/2 -d /mnt/scratch/3 \
-d /mnt/scratch/4 -d /mnt/scratch/5 \
-d /mnt/scratch/6 -d /mnt/scratch/7 \
-d /mnt/scratch/8 -d /mnt/scratch/9 \
-d /mnt/scratch/10 -d /mnt/scratch/11 \
-d /mnt/scratch/12 -d /mnt/scratch/13 \
-d /mnt/scratch/14 -d /mnt/scratch/15
and indeed is hammers the system with many high order GFP_NOFS requests as
per a simle tracepoint during the load:
$ echo '!(gfp_flags & 0x80) && (gfp_flags &0x400000)' > $TRACE_MNT/events/kmem/mm_page_alloc/filter
I am getting
5287609 order=0
37 order=1
1594905 order=2
3048439 order=3
6699207 order=4
66645 order=5
My testing was done in a kvm guest so performance numbers should be
taken with a grain of salt but there seems to be a difference when the
patch is applied:
* Original kernel
FSUse% Count Size Files/sec App Overhead
1 1600000 0 4300.1 20745838
3 3200000 0 4239.9 23849857
5 4800000 0 4243.4 25939543
6 6400000 0 4248.4 19514050
8 8000000 0 4262.1 20796169
9 9600000 0 4257.6 21288675
11 11200000 0 4259.7 19375120
13 12800000 0 4220.7 22734141
14 14400000 0 4238.5 31936458
16 16000000 0 4231.5 23409901
18 17600000 0 4045.3 23577700
19 19200000 0 2783.4 58299526
21 20800000 0 2678.2 40616302
23 22400000 0 2693.5 83973996
and xfs complaining about memory allocation not making progress
[ 2304.372647] XFS: fs_mark(3289) possible memory allocation deadlock size 65624 in kmem_alloc (mode:0x2408240)
[ 2304.443323] XFS: fs_mark(3285) possible memory allocation deadlock size 65728 in kmem_alloc (mode:0x2408240)
[ 4796.772477] XFS: fs_mark(3424) possible memory allocation deadlock size 46936 in kmem_alloc (mode:0x2408240)
[ 4796.775329] XFS: fs_mark(3423) possible memory allocation deadlock size 51416 in kmem_alloc (mode:0x2408240)
[ 4797.388808] XFS: fs_mark(3424) possible memory allocation deadlock size 65728 in kmem_alloc (mode:0x2408240)
* Patched kernel
FSUse% Count Size Files/sec App Overhead
1 1600000 0 4289.1 19243934
3 3200000 0 4241.6 32828865
5 4800000 0 4248.7 32884693
6 6400000 0 4314.4 19608921
8 8000000 0 4269.9 24953292
9 9600000 0 4270.7 33235572
11 11200000 0 4346.4 40817101
13 12800000 0 4285.3 29972397
14 14400000 0 4297.2 20539765
16 16000000 0 4219.6 18596767
18 17600000 0 4273.8 49611187
19 19200000 0 4300.4 27944451
21 20800000 0 4270.6 22324585
22 22400000 0 4317.6 22650382
24 24000000 0 4065.2 22297964
So the dropdown at Count 19200000 didn't happen and there was only a
single warning about allocation not making progress
[ 3063.815003] XFS: fs_mark(3272) possible memory allocation deadlock size 65624 in kmem_alloc (mode:0x2408240)
This suggests that the patch has helped even though there is not all that
much of anonymous memory as the workload mostly generates fs metadata. I
assume the success rate would be higher with more anonymous memory which
should be the case in many workloads.
[akpm@linux-foundation.org: fix comment]
Link: http://lkml.kernel.org/r/20161012114721.31853-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2074 lines
56 KiB
C
2074 lines
56 KiB
C
/*
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* linux/mm/compaction.c
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*
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* Memory compaction for the reduction of external fragmentation. Note that
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* this heavily depends upon page migration to do all the real heavy
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* lifting
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*
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* Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
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*/
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#include <linux/cpu.h>
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#include <linux/swap.h>
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#include <linux/migrate.h>
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#include <linux/compaction.h>
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#include <linux/mm_inline.h>
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#include <linux/backing-dev.h>
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#include <linux/sysctl.h>
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#include <linux/sysfs.h>
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#include <linux/page-isolation.h>
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#include <linux/kasan.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/page_owner.h>
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#include "internal.h"
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#ifdef CONFIG_COMPACTION
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static inline void count_compact_event(enum vm_event_item item)
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{
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count_vm_event(item);
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}
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static inline void count_compact_events(enum vm_event_item item, long delta)
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{
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count_vm_events(item, delta);
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}
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#else
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#define count_compact_event(item) do { } while (0)
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#define count_compact_events(item, delta) do { } while (0)
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#endif
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#if defined CONFIG_COMPACTION || defined CONFIG_CMA
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#define CREATE_TRACE_POINTS
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#include <trace/events/compaction.h>
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#define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
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#define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
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#define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order)
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#define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order)
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static unsigned long release_freepages(struct list_head *freelist)
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{
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struct page *page, *next;
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unsigned long high_pfn = 0;
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list_for_each_entry_safe(page, next, freelist, lru) {
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unsigned long pfn = page_to_pfn(page);
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list_del(&page->lru);
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__free_page(page);
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if (pfn > high_pfn)
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high_pfn = pfn;
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}
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return high_pfn;
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}
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static void map_pages(struct list_head *list)
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{
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unsigned int i, order, nr_pages;
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struct page *page, *next;
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LIST_HEAD(tmp_list);
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list_for_each_entry_safe(page, next, list, lru) {
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list_del(&page->lru);
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order = page_private(page);
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nr_pages = 1 << order;
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post_alloc_hook(page, order, __GFP_MOVABLE);
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if (order)
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split_page(page, order);
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for (i = 0; i < nr_pages; i++) {
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list_add(&page->lru, &tmp_list);
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page++;
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}
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}
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list_splice(&tmp_list, list);
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}
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static inline bool migrate_async_suitable(int migratetype)
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{
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return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
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}
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#ifdef CONFIG_COMPACTION
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int PageMovable(struct page *page)
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{
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struct address_space *mapping;
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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if (!__PageMovable(page))
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return 0;
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mapping = page_mapping(page);
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if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
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return 1;
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return 0;
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}
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EXPORT_SYMBOL(PageMovable);
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void __SetPageMovable(struct page *page, struct address_space *mapping)
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{
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
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page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
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}
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EXPORT_SYMBOL(__SetPageMovable);
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void __ClearPageMovable(struct page *page)
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{
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE(!PageMovable(page), page);
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/*
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* Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
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* flag so that VM can catch up released page by driver after isolation.
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* With it, VM migration doesn't try to put it back.
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*/
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page->mapping = (void *)((unsigned long)page->mapping &
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PAGE_MAPPING_MOVABLE);
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}
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EXPORT_SYMBOL(__ClearPageMovable);
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/* Do not skip compaction more than 64 times */
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#define COMPACT_MAX_DEFER_SHIFT 6
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/*
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* Compaction is deferred when compaction fails to result in a page
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* allocation success. 1 << compact_defer_limit compactions are skipped up
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* to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
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*/
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void defer_compaction(struct zone *zone, int order)
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{
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zone->compact_considered = 0;
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zone->compact_defer_shift++;
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if (order < zone->compact_order_failed)
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zone->compact_order_failed = order;
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if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
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zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
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trace_mm_compaction_defer_compaction(zone, order);
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}
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/* Returns true if compaction should be skipped this time */
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bool compaction_deferred(struct zone *zone, int order)
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{
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unsigned long defer_limit = 1UL << zone->compact_defer_shift;
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if (order < zone->compact_order_failed)
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return false;
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/* Avoid possible overflow */
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if (++zone->compact_considered > defer_limit)
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zone->compact_considered = defer_limit;
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if (zone->compact_considered >= defer_limit)
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return false;
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trace_mm_compaction_deferred(zone, order);
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return true;
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}
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/*
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* Update defer tracking counters after successful compaction of given order,
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* which means an allocation either succeeded (alloc_success == true) or is
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* expected to succeed.
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*/
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void compaction_defer_reset(struct zone *zone, int order,
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bool alloc_success)
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{
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if (alloc_success) {
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zone->compact_considered = 0;
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zone->compact_defer_shift = 0;
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}
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if (order >= zone->compact_order_failed)
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zone->compact_order_failed = order + 1;
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trace_mm_compaction_defer_reset(zone, order);
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}
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/* Returns true if restarting compaction after many failures */
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bool compaction_restarting(struct zone *zone, int order)
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{
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if (order < zone->compact_order_failed)
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return false;
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return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
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zone->compact_considered >= 1UL << zone->compact_defer_shift;
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}
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/* Returns true if the pageblock should be scanned for pages to isolate. */
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static inline bool isolation_suitable(struct compact_control *cc,
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struct page *page)
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{
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if (cc->ignore_skip_hint)
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return true;
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return !get_pageblock_skip(page);
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}
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static void reset_cached_positions(struct zone *zone)
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{
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zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
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zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
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zone->compact_cached_free_pfn =
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pageblock_start_pfn(zone_end_pfn(zone) - 1);
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}
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/*
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* This function is called to clear all cached information on pageblocks that
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* should be skipped for page isolation when the migrate and free page scanner
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* meet.
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*/
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static void __reset_isolation_suitable(struct zone *zone)
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{
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unsigned long start_pfn = zone->zone_start_pfn;
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unsigned long end_pfn = zone_end_pfn(zone);
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unsigned long pfn;
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zone->compact_blockskip_flush = false;
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/* Walk the zone and mark every pageblock as suitable for isolation */
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for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
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struct page *page;
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cond_resched();
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if (!pfn_valid(pfn))
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continue;
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page = pfn_to_page(pfn);
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if (zone != page_zone(page))
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continue;
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clear_pageblock_skip(page);
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}
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reset_cached_positions(zone);
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}
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void reset_isolation_suitable(pg_data_t *pgdat)
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{
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int zoneid;
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for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
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struct zone *zone = &pgdat->node_zones[zoneid];
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if (!populated_zone(zone))
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continue;
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/* Only flush if a full compaction finished recently */
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if (zone->compact_blockskip_flush)
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__reset_isolation_suitable(zone);
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}
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}
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/*
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* If no pages were isolated then mark this pageblock to be skipped in the
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* future. The information is later cleared by __reset_isolation_suitable().
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*/
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static void update_pageblock_skip(struct compact_control *cc,
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struct page *page, unsigned long nr_isolated,
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bool migrate_scanner)
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{
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struct zone *zone = cc->zone;
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unsigned long pfn;
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if (cc->ignore_skip_hint)
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return;
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if (!page)
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return;
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if (nr_isolated)
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return;
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set_pageblock_skip(page);
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pfn = page_to_pfn(page);
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/* Update where async and sync compaction should restart */
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if (migrate_scanner) {
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if (pfn > zone->compact_cached_migrate_pfn[0])
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zone->compact_cached_migrate_pfn[0] = pfn;
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if (cc->mode != MIGRATE_ASYNC &&
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pfn > zone->compact_cached_migrate_pfn[1])
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zone->compact_cached_migrate_pfn[1] = pfn;
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} else {
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if (pfn < zone->compact_cached_free_pfn)
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zone->compact_cached_free_pfn = pfn;
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}
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}
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#else
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static inline bool isolation_suitable(struct compact_control *cc,
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struct page *page)
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{
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return true;
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}
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static void update_pageblock_skip(struct compact_control *cc,
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struct page *page, unsigned long nr_isolated,
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bool migrate_scanner)
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{
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}
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#endif /* CONFIG_COMPACTION */
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/*
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* Compaction requires the taking of some coarse locks that are potentially
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* very heavily contended. For async compaction, back out if the lock cannot
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* be taken immediately. For sync compaction, spin on the lock if needed.
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*
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* Returns true if the lock is held
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* Returns false if the lock is not held and compaction should abort
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*/
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static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
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struct compact_control *cc)
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{
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if (cc->mode == MIGRATE_ASYNC) {
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if (!spin_trylock_irqsave(lock, *flags)) {
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cc->contended = true;
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return false;
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}
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} else {
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spin_lock_irqsave(lock, *flags);
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}
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return true;
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}
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/*
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* Compaction requires the taking of some coarse locks that are potentially
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* very heavily contended. The lock should be periodically unlocked to avoid
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* having disabled IRQs for a long time, even when there is nobody waiting on
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* the lock. It might also be that allowing the IRQs will result in
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* need_resched() becoming true. If scheduling is needed, async compaction
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* aborts. Sync compaction schedules.
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* Either compaction type will also abort if a fatal signal is pending.
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* In either case if the lock was locked, it is dropped and not regained.
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*
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* Returns true if compaction should abort due to fatal signal pending, or
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* async compaction due to need_resched()
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* Returns false when compaction can continue (sync compaction might have
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* scheduled)
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*/
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static bool compact_unlock_should_abort(spinlock_t *lock,
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unsigned long flags, bool *locked, struct compact_control *cc)
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{
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if (*locked) {
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spin_unlock_irqrestore(lock, flags);
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*locked = false;
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}
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if (fatal_signal_pending(current)) {
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cc->contended = true;
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return true;
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}
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if (need_resched()) {
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if (cc->mode == MIGRATE_ASYNC) {
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cc->contended = true;
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return true;
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}
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cond_resched();
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}
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return false;
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}
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/*
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* Aside from avoiding lock contention, compaction also periodically checks
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* need_resched() and either schedules in sync compaction or aborts async
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* compaction. This is similar to what compact_unlock_should_abort() does, but
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* is used where no lock is concerned.
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*
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* Returns false when no scheduling was needed, or sync compaction scheduled.
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* Returns true when async compaction should abort.
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*/
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static inline bool compact_should_abort(struct compact_control *cc)
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{
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/* async compaction aborts if contended */
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if (need_resched()) {
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if (cc->mode == MIGRATE_ASYNC) {
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cc->contended = true;
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return true;
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}
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cond_resched();
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}
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return false;
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}
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/*
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* Isolate free pages onto a private freelist. If @strict is true, will abort
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* returning 0 on any invalid PFNs or non-free pages inside of the pageblock
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* (even though it may still end up isolating some pages).
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*/
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static unsigned long isolate_freepages_block(struct compact_control *cc,
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unsigned long *start_pfn,
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unsigned long end_pfn,
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struct list_head *freelist,
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bool strict)
|
|
{
|
|
int nr_scanned = 0, total_isolated = 0;
|
|
struct page *cursor, *valid_page = NULL;
|
|
unsigned long flags = 0;
|
|
bool locked = false;
|
|
unsigned long blockpfn = *start_pfn;
|
|
unsigned int order;
|
|
|
|
cursor = pfn_to_page(blockpfn);
|
|
|
|
/* Isolate free pages. */
|
|
for (; blockpfn < end_pfn; blockpfn++, cursor++) {
|
|
int isolated;
|
|
struct page *page = cursor;
|
|
|
|
/*
|
|
* Periodically drop the lock (if held) regardless of its
|
|
* contention, to give chance to IRQs. Abort if fatal signal
|
|
* pending or async compaction detects need_resched()
|
|
*/
|
|
if (!(blockpfn % SWAP_CLUSTER_MAX)
|
|
&& compact_unlock_should_abort(&cc->zone->lock, flags,
|
|
&locked, cc))
|
|
break;
|
|
|
|
nr_scanned++;
|
|
if (!pfn_valid_within(blockpfn))
|
|
goto isolate_fail;
|
|
|
|
if (!valid_page)
|
|
valid_page = page;
|
|
|
|
/*
|
|
* For compound pages such as THP and hugetlbfs, we can save
|
|
* potentially a lot of iterations if we skip them at once.
|
|
* The check is racy, but we can consider only valid values
|
|
* and the only danger is skipping too much.
|
|
*/
|
|
if (PageCompound(page)) {
|
|
unsigned int comp_order = compound_order(page);
|
|
|
|
if (likely(comp_order < MAX_ORDER)) {
|
|
blockpfn += (1UL << comp_order) - 1;
|
|
cursor += (1UL << comp_order) - 1;
|
|
}
|
|
|
|
goto isolate_fail;
|
|
}
|
|
|
|
if (!PageBuddy(page))
|
|
goto isolate_fail;
|
|
|
|
/*
|
|
* If we already hold the lock, we can skip some rechecking.
|
|
* Note that if we hold the lock now, checked_pageblock was
|
|
* already set in some previous iteration (or strict is true),
|
|
* so it is correct to skip the suitable migration target
|
|
* recheck as well.
|
|
*/
|
|
if (!locked) {
|
|
/*
|
|
* The zone lock must be held to isolate freepages.
|
|
* Unfortunately this is a very coarse lock and can be
|
|
* heavily contended if there are parallel allocations
|
|
* or parallel compactions. For async compaction do not
|
|
* spin on the lock and we acquire the lock as late as
|
|
* possible.
|
|
*/
|
|
locked = compact_trylock_irqsave(&cc->zone->lock,
|
|
&flags, cc);
|
|
if (!locked)
|
|
break;
|
|
|
|
/* Recheck this is a buddy page under lock */
|
|
if (!PageBuddy(page))
|
|
goto isolate_fail;
|
|
}
|
|
|
|
/* Found a free page, will break it into order-0 pages */
|
|
order = page_order(page);
|
|
isolated = __isolate_free_page(page, order);
|
|
if (!isolated)
|
|
break;
|
|
set_page_private(page, order);
|
|
|
|
total_isolated += isolated;
|
|
cc->nr_freepages += isolated;
|
|
list_add_tail(&page->lru, freelist);
|
|
|
|
if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
|
|
blockpfn += isolated;
|
|
break;
|
|
}
|
|
/* Advance to the end of split page */
|
|
blockpfn += isolated - 1;
|
|
cursor += isolated - 1;
|
|
continue;
|
|
|
|
isolate_fail:
|
|
if (strict)
|
|
break;
|
|
else
|
|
continue;
|
|
|
|
}
|
|
|
|
if (locked)
|
|
spin_unlock_irqrestore(&cc->zone->lock, flags);
|
|
|
|
/*
|
|
* There is a tiny chance that we have read bogus compound_order(),
|
|
* so be careful to not go outside of the pageblock.
|
|
*/
|
|
if (unlikely(blockpfn > end_pfn))
|
|
blockpfn = end_pfn;
|
|
|
|
trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
|
|
nr_scanned, total_isolated);
|
|
|
|
/* Record how far we have got within the block */
|
|
*start_pfn = blockpfn;
|
|
|
|
/*
|
|
* If strict isolation is requested by CMA then check that all the
|
|
* pages requested were isolated. If there were any failures, 0 is
|
|
* returned and CMA will fail.
|
|
*/
|
|
if (strict && blockpfn < end_pfn)
|
|
total_isolated = 0;
|
|
|
|
/* Update the pageblock-skip if the whole pageblock was scanned */
|
|
if (blockpfn == end_pfn)
|
|
update_pageblock_skip(cc, valid_page, total_isolated, false);
|
|
|
|
count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
|
|
if (total_isolated)
|
|
count_compact_events(COMPACTISOLATED, total_isolated);
|
|
return total_isolated;
|
|
}
|
|
|
|
/**
|
|
* isolate_freepages_range() - isolate free pages.
|
|
* @start_pfn: The first PFN to start isolating.
|
|
* @end_pfn: The one-past-last PFN.
|
|
*
|
|
* Non-free pages, invalid PFNs, or zone boundaries within the
|
|
* [start_pfn, end_pfn) range are considered errors, cause function to
|
|
* undo its actions and return zero.
|
|
*
|
|
* Otherwise, function returns one-past-the-last PFN of isolated page
|
|
* (which may be greater then end_pfn if end fell in a middle of
|
|
* a free page).
|
|
*/
|
|
unsigned long
|
|
isolate_freepages_range(struct compact_control *cc,
|
|
unsigned long start_pfn, unsigned long end_pfn)
|
|
{
|
|
unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
|
|
LIST_HEAD(freelist);
|
|
|
|
pfn = start_pfn;
|
|
block_start_pfn = pageblock_start_pfn(pfn);
|
|
if (block_start_pfn < cc->zone->zone_start_pfn)
|
|
block_start_pfn = cc->zone->zone_start_pfn;
|
|
block_end_pfn = pageblock_end_pfn(pfn);
|
|
|
|
for (; pfn < end_pfn; pfn += isolated,
|
|
block_start_pfn = block_end_pfn,
|
|
block_end_pfn += pageblock_nr_pages) {
|
|
/* Protect pfn from changing by isolate_freepages_block */
|
|
unsigned long isolate_start_pfn = pfn;
|
|
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
|
|
/*
|
|
* pfn could pass the block_end_pfn if isolated freepage
|
|
* is more than pageblock order. In this case, we adjust
|
|
* scanning range to right one.
|
|
*/
|
|
if (pfn >= block_end_pfn) {
|
|
block_start_pfn = pageblock_start_pfn(pfn);
|
|
block_end_pfn = pageblock_end_pfn(pfn);
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
}
|
|
|
|
if (!pageblock_pfn_to_page(block_start_pfn,
|
|
block_end_pfn, cc->zone))
|
|
break;
|
|
|
|
isolated = isolate_freepages_block(cc, &isolate_start_pfn,
|
|
block_end_pfn, &freelist, true);
|
|
|
|
/*
|
|
* In strict mode, isolate_freepages_block() returns 0 if
|
|
* there are any holes in the block (ie. invalid PFNs or
|
|
* non-free pages).
|
|
*/
|
|
if (!isolated)
|
|
break;
|
|
|
|
/*
|
|
* If we managed to isolate pages, it is always (1 << n) *
|
|
* pageblock_nr_pages for some non-negative n. (Max order
|
|
* page may span two pageblocks).
|
|
*/
|
|
}
|
|
|
|
/* __isolate_free_page() does not map the pages */
|
|
map_pages(&freelist);
|
|
|
|
if (pfn < end_pfn) {
|
|
/* Loop terminated early, cleanup. */
|
|
release_freepages(&freelist);
|
|
return 0;
|
|
}
|
|
|
|
/* We don't use freelists for anything. */
|
|
return pfn;
|
|
}
|
|
|
|
/* Similar to reclaim, but different enough that they don't share logic */
|
|
static bool too_many_isolated(struct zone *zone)
|
|
{
|
|
unsigned long active, inactive, isolated;
|
|
|
|
inactive = node_page_state(zone->zone_pgdat, NR_INACTIVE_FILE) +
|
|
node_page_state(zone->zone_pgdat, NR_INACTIVE_ANON);
|
|
active = node_page_state(zone->zone_pgdat, NR_ACTIVE_FILE) +
|
|
node_page_state(zone->zone_pgdat, NR_ACTIVE_ANON);
|
|
isolated = node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE) +
|
|
node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON);
|
|
|
|
return isolated > (inactive + active) / 2;
|
|
}
|
|
|
|
/**
|
|
* isolate_migratepages_block() - isolate all migrate-able pages within
|
|
* a single pageblock
|
|
* @cc: Compaction control structure.
|
|
* @low_pfn: The first PFN to isolate
|
|
* @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
|
|
* @isolate_mode: Isolation mode to be used.
|
|
*
|
|
* Isolate all pages that can be migrated from the range specified by
|
|
* [low_pfn, end_pfn). The range is expected to be within same pageblock.
|
|
* Returns zero if there is a fatal signal pending, otherwise PFN of the
|
|
* first page that was not scanned (which may be both less, equal to or more
|
|
* than end_pfn).
|
|
*
|
|
* The pages are isolated on cc->migratepages list (not required to be empty),
|
|
* and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
|
|
* is neither read nor updated.
|
|
*/
|
|
static unsigned long
|
|
isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
|
|
unsigned long end_pfn, isolate_mode_t isolate_mode)
|
|
{
|
|
struct zone *zone = cc->zone;
|
|
unsigned long nr_scanned = 0, nr_isolated = 0;
|
|
struct lruvec *lruvec;
|
|
unsigned long flags = 0;
|
|
bool locked = false;
|
|
struct page *page = NULL, *valid_page = NULL;
|
|
unsigned long start_pfn = low_pfn;
|
|
bool skip_on_failure = false;
|
|
unsigned long next_skip_pfn = 0;
|
|
|
|
/*
|
|
* Ensure that there are not too many pages isolated from the LRU
|
|
* list by either parallel reclaimers or compaction. If there are,
|
|
* delay for some time until fewer pages are isolated
|
|
*/
|
|
while (unlikely(too_many_isolated(zone))) {
|
|
/* async migration should just abort */
|
|
if (cc->mode == MIGRATE_ASYNC)
|
|
return 0;
|
|
|
|
congestion_wait(BLK_RW_ASYNC, HZ/10);
|
|
|
|
if (fatal_signal_pending(current))
|
|
return 0;
|
|
}
|
|
|
|
if (compact_should_abort(cc))
|
|
return 0;
|
|
|
|
if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
|
|
skip_on_failure = true;
|
|
next_skip_pfn = block_end_pfn(low_pfn, cc->order);
|
|
}
|
|
|
|
/* Time to isolate some pages for migration */
|
|
for (; low_pfn < end_pfn; low_pfn++) {
|
|
|
|
if (skip_on_failure && low_pfn >= next_skip_pfn) {
|
|
/*
|
|
* We have isolated all migration candidates in the
|
|
* previous order-aligned block, and did not skip it due
|
|
* to failure. We should migrate the pages now and
|
|
* hopefully succeed compaction.
|
|
*/
|
|
if (nr_isolated)
|
|
break;
|
|
|
|
/*
|
|
* We failed to isolate in the previous order-aligned
|
|
* block. Set the new boundary to the end of the
|
|
* current block. Note we can't simply increase
|
|
* next_skip_pfn by 1 << order, as low_pfn might have
|
|
* been incremented by a higher number due to skipping
|
|
* a compound or a high-order buddy page in the
|
|
* previous loop iteration.
|
|
*/
|
|
next_skip_pfn = block_end_pfn(low_pfn, cc->order);
|
|
}
|
|
|
|
/*
|
|
* Periodically drop the lock (if held) regardless of its
|
|
* contention, to give chance to IRQs. Abort async compaction
|
|
* if contended.
|
|
*/
|
|
if (!(low_pfn % SWAP_CLUSTER_MAX)
|
|
&& compact_unlock_should_abort(zone_lru_lock(zone), flags,
|
|
&locked, cc))
|
|
break;
|
|
|
|
if (!pfn_valid_within(low_pfn))
|
|
goto isolate_fail;
|
|
nr_scanned++;
|
|
|
|
page = pfn_to_page(low_pfn);
|
|
|
|
if (!valid_page)
|
|
valid_page = page;
|
|
|
|
/*
|
|
* Skip if free. We read page order here without zone lock
|
|
* which is generally unsafe, but the race window is small and
|
|
* the worst thing that can happen is that we skip some
|
|
* potential isolation targets.
|
|
*/
|
|
if (PageBuddy(page)) {
|
|
unsigned long freepage_order = page_order_unsafe(page);
|
|
|
|
/*
|
|
* Without lock, we cannot be sure that what we got is
|
|
* a valid page order. Consider only values in the
|
|
* valid order range to prevent low_pfn overflow.
|
|
*/
|
|
if (freepage_order > 0 && freepage_order < MAX_ORDER)
|
|
low_pfn += (1UL << freepage_order) - 1;
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Regardless of being on LRU, compound pages such as THP and
|
|
* hugetlbfs are not to be compacted. We can potentially save
|
|
* a lot of iterations if we skip them at once. The check is
|
|
* racy, but we can consider only valid values and the only
|
|
* danger is skipping too much.
|
|
*/
|
|
if (PageCompound(page)) {
|
|
unsigned int comp_order = compound_order(page);
|
|
|
|
if (likely(comp_order < MAX_ORDER))
|
|
low_pfn += (1UL << comp_order) - 1;
|
|
|
|
goto isolate_fail;
|
|
}
|
|
|
|
/*
|
|
* Check may be lockless but that's ok as we recheck later.
|
|
* It's possible to migrate LRU and non-lru movable pages.
|
|
* Skip any other type of page
|
|
*/
|
|
if (!PageLRU(page)) {
|
|
/*
|
|
* __PageMovable can return false positive so we need
|
|
* to verify it under page_lock.
|
|
*/
|
|
if (unlikely(__PageMovable(page)) &&
|
|
!PageIsolated(page)) {
|
|
if (locked) {
|
|
spin_unlock_irqrestore(zone_lru_lock(zone),
|
|
flags);
|
|
locked = false;
|
|
}
|
|
|
|
if (isolate_movable_page(page, isolate_mode))
|
|
goto isolate_success;
|
|
}
|
|
|
|
goto isolate_fail;
|
|
}
|
|
|
|
/*
|
|
* Migration will fail if an anonymous page is pinned in memory,
|
|
* so avoid taking lru_lock and isolating it unnecessarily in an
|
|
* admittedly racy check.
|
|
*/
|
|
if (!page_mapping(page) &&
|
|
page_count(page) > page_mapcount(page))
|
|
goto isolate_fail;
|
|
|
|
/*
|
|
* Only allow to migrate anonymous pages in GFP_NOFS context
|
|
* because those do not depend on fs locks.
|
|
*/
|
|
if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
|
|
goto isolate_fail;
|
|
|
|
/* If we already hold the lock, we can skip some rechecking */
|
|
if (!locked) {
|
|
locked = compact_trylock_irqsave(zone_lru_lock(zone),
|
|
&flags, cc);
|
|
if (!locked)
|
|
break;
|
|
|
|
/* Recheck PageLRU and PageCompound under lock */
|
|
if (!PageLRU(page))
|
|
goto isolate_fail;
|
|
|
|
/*
|
|
* Page become compound since the non-locked check,
|
|
* and it's on LRU. It can only be a THP so the order
|
|
* is safe to read and it's 0 for tail pages.
|
|
*/
|
|
if (unlikely(PageCompound(page))) {
|
|
low_pfn += (1UL << compound_order(page)) - 1;
|
|
goto isolate_fail;
|
|
}
|
|
}
|
|
|
|
lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
|
|
|
|
/* Try isolate the page */
|
|
if (__isolate_lru_page(page, isolate_mode) != 0)
|
|
goto isolate_fail;
|
|
|
|
VM_BUG_ON_PAGE(PageCompound(page), page);
|
|
|
|
/* Successfully isolated */
|
|
del_page_from_lru_list(page, lruvec, page_lru(page));
|
|
inc_node_page_state(page,
|
|
NR_ISOLATED_ANON + page_is_file_cache(page));
|
|
|
|
isolate_success:
|
|
list_add(&page->lru, &cc->migratepages);
|
|
cc->nr_migratepages++;
|
|
nr_isolated++;
|
|
|
|
/*
|
|
* Record where we could have freed pages by migration and not
|
|
* yet flushed them to buddy allocator.
|
|
* - this is the lowest page that was isolated and likely be
|
|
* then freed by migration.
|
|
*/
|
|
if (!cc->last_migrated_pfn)
|
|
cc->last_migrated_pfn = low_pfn;
|
|
|
|
/* Avoid isolating too much */
|
|
if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
|
|
++low_pfn;
|
|
break;
|
|
}
|
|
|
|
continue;
|
|
isolate_fail:
|
|
if (!skip_on_failure)
|
|
continue;
|
|
|
|
/*
|
|
* We have isolated some pages, but then failed. Release them
|
|
* instead of migrating, as we cannot form the cc->order buddy
|
|
* page anyway.
|
|
*/
|
|
if (nr_isolated) {
|
|
if (locked) {
|
|
spin_unlock_irqrestore(zone_lru_lock(zone), flags);
|
|
locked = false;
|
|
}
|
|
putback_movable_pages(&cc->migratepages);
|
|
cc->nr_migratepages = 0;
|
|
cc->last_migrated_pfn = 0;
|
|
nr_isolated = 0;
|
|
}
|
|
|
|
if (low_pfn < next_skip_pfn) {
|
|
low_pfn = next_skip_pfn - 1;
|
|
/*
|
|
* The check near the loop beginning would have updated
|
|
* next_skip_pfn too, but this is a bit simpler.
|
|
*/
|
|
next_skip_pfn += 1UL << cc->order;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* The PageBuddy() check could have potentially brought us outside
|
|
* the range to be scanned.
|
|
*/
|
|
if (unlikely(low_pfn > end_pfn))
|
|
low_pfn = end_pfn;
|
|
|
|
if (locked)
|
|
spin_unlock_irqrestore(zone_lru_lock(zone), flags);
|
|
|
|
/*
|
|
* Update the pageblock-skip information and cached scanner pfn,
|
|
* if the whole pageblock was scanned without isolating any page.
|
|
*/
|
|
if (low_pfn == end_pfn)
|
|
update_pageblock_skip(cc, valid_page, nr_isolated, true);
|
|
|
|
trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
|
|
nr_scanned, nr_isolated);
|
|
|
|
count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
|
|
if (nr_isolated)
|
|
count_compact_events(COMPACTISOLATED, nr_isolated);
|
|
|
|
return low_pfn;
|
|
}
|
|
|
|
/**
|
|
* isolate_migratepages_range() - isolate migrate-able pages in a PFN range
|
|
* @cc: Compaction control structure.
|
|
* @start_pfn: The first PFN to start isolating.
|
|
* @end_pfn: The one-past-last PFN.
|
|
*
|
|
* Returns zero if isolation fails fatally due to e.g. pending signal.
|
|
* Otherwise, function returns one-past-the-last PFN of isolated page
|
|
* (which may be greater than end_pfn if end fell in a middle of a THP page).
|
|
*/
|
|
unsigned long
|
|
isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
|
|
unsigned long end_pfn)
|
|
{
|
|
unsigned long pfn, block_start_pfn, block_end_pfn;
|
|
|
|
/* Scan block by block. First and last block may be incomplete */
|
|
pfn = start_pfn;
|
|
block_start_pfn = pageblock_start_pfn(pfn);
|
|
if (block_start_pfn < cc->zone->zone_start_pfn)
|
|
block_start_pfn = cc->zone->zone_start_pfn;
|
|
block_end_pfn = pageblock_end_pfn(pfn);
|
|
|
|
for (; pfn < end_pfn; pfn = block_end_pfn,
|
|
block_start_pfn = block_end_pfn,
|
|
block_end_pfn += pageblock_nr_pages) {
|
|
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
|
|
if (!pageblock_pfn_to_page(block_start_pfn,
|
|
block_end_pfn, cc->zone))
|
|
continue;
|
|
|
|
pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
|
|
ISOLATE_UNEVICTABLE);
|
|
|
|
if (!pfn)
|
|
break;
|
|
|
|
if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
|
|
break;
|
|
}
|
|
|
|
return pfn;
|
|
}
|
|
|
|
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
|
|
#ifdef CONFIG_COMPACTION
|
|
|
|
/* Returns true if the page is within a block suitable for migration to */
|
|
static bool suitable_migration_target(struct compact_control *cc,
|
|
struct page *page)
|
|
{
|
|
if (cc->ignore_block_suitable)
|
|
return true;
|
|
|
|
/* If the page is a large free page, then disallow migration */
|
|
if (PageBuddy(page)) {
|
|
/*
|
|
* We are checking page_order without zone->lock taken. But
|
|
* the only small danger is that we skip a potentially suitable
|
|
* pageblock, so it's not worth to check order for valid range.
|
|
*/
|
|
if (page_order_unsafe(page) >= pageblock_order)
|
|
return false;
|
|
}
|
|
|
|
/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
|
|
if (migrate_async_suitable(get_pageblock_migratetype(page)))
|
|
return true;
|
|
|
|
/* Otherwise skip the block */
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Test whether the free scanner has reached the same or lower pageblock than
|
|
* the migration scanner, and compaction should thus terminate.
|
|
*/
|
|
static inline bool compact_scanners_met(struct compact_control *cc)
|
|
{
|
|
return (cc->free_pfn >> pageblock_order)
|
|
<= (cc->migrate_pfn >> pageblock_order);
|
|
}
|
|
|
|
/*
|
|
* Based on information in the current compact_control, find blocks
|
|
* suitable for isolating free pages from and then isolate them.
|
|
*/
|
|
static void isolate_freepages(struct compact_control *cc)
|
|
{
|
|
struct zone *zone = cc->zone;
|
|
struct page *page;
|
|
unsigned long block_start_pfn; /* start of current pageblock */
|
|
unsigned long isolate_start_pfn; /* exact pfn we start at */
|
|
unsigned long block_end_pfn; /* end of current pageblock */
|
|
unsigned long low_pfn; /* lowest pfn scanner is able to scan */
|
|
struct list_head *freelist = &cc->freepages;
|
|
|
|
/*
|
|
* Initialise the free scanner. The starting point is where we last
|
|
* successfully isolated from, zone-cached value, or the end of the
|
|
* zone when isolating for the first time. For looping we also need
|
|
* this pfn aligned down to the pageblock boundary, because we do
|
|
* block_start_pfn -= pageblock_nr_pages in the for loop.
|
|
* For ending point, take care when isolating in last pageblock of a
|
|
* a zone which ends in the middle of a pageblock.
|
|
* The low boundary is the end of the pageblock the migration scanner
|
|
* is using.
|
|
*/
|
|
isolate_start_pfn = cc->free_pfn;
|
|
block_start_pfn = pageblock_start_pfn(cc->free_pfn);
|
|
block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
|
|
zone_end_pfn(zone));
|
|
low_pfn = pageblock_end_pfn(cc->migrate_pfn);
|
|
|
|
/*
|
|
* Isolate free pages until enough are available to migrate the
|
|
* pages on cc->migratepages. We stop searching if the migrate
|
|
* and free page scanners meet or enough free pages are isolated.
|
|
*/
|
|
for (; block_start_pfn >= low_pfn;
|
|
block_end_pfn = block_start_pfn,
|
|
block_start_pfn -= pageblock_nr_pages,
|
|
isolate_start_pfn = block_start_pfn) {
|
|
/*
|
|
* This can iterate a massively long zone without finding any
|
|
* suitable migration targets, so periodically check if we need
|
|
* to schedule, or even abort async compaction.
|
|
*/
|
|
if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
|
|
&& compact_should_abort(cc))
|
|
break;
|
|
|
|
page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
|
|
zone);
|
|
if (!page)
|
|
continue;
|
|
|
|
/* Check the block is suitable for migration */
|
|
if (!suitable_migration_target(cc, page))
|
|
continue;
|
|
|
|
/* If isolation recently failed, do not retry */
|
|
if (!isolation_suitable(cc, page))
|
|
continue;
|
|
|
|
/* Found a block suitable for isolating free pages from. */
|
|
isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn,
|
|
freelist, false);
|
|
|
|
/*
|
|
* If we isolated enough freepages, or aborted due to lock
|
|
* contention, terminate.
|
|
*/
|
|
if ((cc->nr_freepages >= cc->nr_migratepages)
|
|
|| cc->contended) {
|
|
if (isolate_start_pfn >= block_end_pfn) {
|
|
/*
|
|
* Restart at previous pageblock if more
|
|
* freepages can be isolated next time.
|
|
*/
|
|
isolate_start_pfn =
|
|
block_start_pfn - pageblock_nr_pages;
|
|
}
|
|
break;
|
|
} else if (isolate_start_pfn < block_end_pfn) {
|
|
/*
|
|
* If isolation failed early, do not continue
|
|
* needlessly.
|
|
*/
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* __isolate_free_page() does not map the pages */
|
|
map_pages(freelist);
|
|
|
|
/*
|
|
* Record where the free scanner will restart next time. Either we
|
|
* broke from the loop and set isolate_start_pfn based on the last
|
|
* call to isolate_freepages_block(), or we met the migration scanner
|
|
* and the loop terminated due to isolate_start_pfn < low_pfn
|
|
*/
|
|
cc->free_pfn = isolate_start_pfn;
|
|
}
|
|
|
|
/*
|
|
* This is a migrate-callback that "allocates" freepages by taking pages
|
|
* from the isolated freelists in the block we are migrating to.
|
|
*/
|
|
static struct page *compaction_alloc(struct page *migratepage,
|
|
unsigned long data,
|
|
int **result)
|
|
{
|
|
struct compact_control *cc = (struct compact_control *)data;
|
|
struct page *freepage;
|
|
|
|
/*
|
|
* Isolate free pages if necessary, and if we are not aborting due to
|
|
* contention.
|
|
*/
|
|
if (list_empty(&cc->freepages)) {
|
|
if (!cc->contended)
|
|
isolate_freepages(cc);
|
|
|
|
if (list_empty(&cc->freepages))
|
|
return NULL;
|
|
}
|
|
|
|
freepage = list_entry(cc->freepages.next, struct page, lru);
|
|
list_del(&freepage->lru);
|
|
cc->nr_freepages--;
|
|
|
|
return freepage;
|
|
}
|
|
|
|
/*
|
|
* This is a migrate-callback that "frees" freepages back to the isolated
|
|
* freelist. All pages on the freelist are from the same zone, so there is no
|
|
* special handling needed for NUMA.
|
|
*/
|
|
static void compaction_free(struct page *page, unsigned long data)
|
|
{
|
|
struct compact_control *cc = (struct compact_control *)data;
|
|
|
|
list_add(&page->lru, &cc->freepages);
|
|
cc->nr_freepages++;
|
|
}
|
|
|
|
/* possible outcome of isolate_migratepages */
|
|
typedef enum {
|
|
ISOLATE_ABORT, /* Abort compaction now */
|
|
ISOLATE_NONE, /* No pages isolated, continue scanning */
|
|
ISOLATE_SUCCESS, /* Pages isolated, migrate */
|
|
} isolate_migrate_t;
|
|
|
|
/*
|
|
* Allow userspace to control policy on scanning the unevictable LRU for
|
|
* compactable pages.
|
|
*/
|
|
int sysctl_compact_unevictable_allowed __read_mostly = 1;
|
|
|
|
/*
|
|
* Isolate all pages that can be migrated from the first suitable block,
|
|
* starting at the block pointed to by the migrate scanner pfn within
|
|
* compact_control.
|
|
*/
|
|
static isolate_migrate_t isolate_migratepages(struct zone *zone,
|
|
struct compact_control *cc)
|
|
{
|
|
unsigned long block_start_pfn;
|
|
unsigned long block_end_pfn;
|
|
unsigned long low_pfn;
|
|
struct page *page;
|
|
const isolate_mode_t isolate_mode =
|
|
(sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
|
|
(cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
|
|
|
|
/*
|
|
* Start at where we last stopped, or beginning of the zone as
|
|
* initialized by compact_zone()
|
|
*/
|
|
low_pfn = cc->migrate_pfn;
|
|
block_start_pfn = pageblock_start_pfn(low_pfn);
|
|
if (block_start_pfn < zone->zone_start_pfn)
|
|
block_start_pfn = zone->zone_start_pfn;
|
|
|
|
/* Only scan within a pageblock boundary */
|
|
block_end_pfn = pageblock_end_pfn(low_pfn);
|
|
|
|
/*
|
|
* Iterate over whole pageblocks until we find the first suitable.
|
|
* Do not cross the free scanner.
|
|
*/
|
|
for (; block_end_pfn <= cc->free_pfn;
|
|
low_pfn = block_end_pfn,
|
|
block_start_pfn = block_end_pfn,
|
|
block_end_pfn += pageblock_nr_pages) {
|
|
|
|
/*
|
|
* This can potentially iterate a massively long zone with
|
|
* many pageblocks unsuitable, so periodically check if we
|
|
* need to schedule, or even abort async compaction.
|
|
*/
|
|
if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
|
|
&& compact_should_abort(cc))
|
|
break;
|
|
|
|
page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
|
|
zone);
|
|
if (!page)
|
|
continue;
|
|
|
|
/* If isolation recently failed, do not retry */
|
|
if (!isolation_suitable(cc, page))
|
|
continue;
|
|
|
|
/*
|
|
* For async compaction, also only scan in MOVABLE blocks.
|
|
* Async compaction is optimistic to see if the minimum amount
|
|
* of work satisfies the allocation.
|
|
*/
|
|
if (cc->mode == MIGRATE_ASYNC &&
|
|
!migrate_async_suitable(get_pageblock_migratetype(page)))
|
|
continue;
|
|
|
|
/* Perform the isolation */
|
|
low_pfn = isolate_migratepages_block(cc, low_pfn,
|
|
block_end_pfn, isolate_mode);
|
|
|
|
if (!low_pfn || cc->contended)
|
|
return ISOLATE_ABORT;
|
|
|
|
/*
|
|
* Either we isolated something and proceed with migration. Or
|
|
* we failed and compact_zone should decide if we should
|
|
* continue or not.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
/* Record where migration scanner will be restarted. */
|
|
cc->migrate_pfn = low_pfn;
|
|
|
|
return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
|
|
}
|
|
|
|
/*
|
|
* order == -1 is expected when compacting via
|
|
* /proc/sys/vm/compact_memory
|
|
*/
|
|
static inline bool is_via_compact_memory(int order)
|
|
{
|
|
return order == -1;
|
|
}
|
|
|
|
static enum compact_result __compact_finished(struct zone *zone, struct compact_control *cc,
|
|
const int migratetype)
|
|
{
|
|
unsigned int order;
|
|
unsigned long watermark;
|
|
|
|
if (cc->contended || fatal_signal_pending(current))
|
|
return COMPACT_CONTENDED;
|
|
|
|
/* Compaction run completes if the migrate and free scanner meet */
|
|
if (compact_scanners_met(cc)) {
|
|
/* Let the next compaction start anew. */
|
|
reset_cached_positions(zone);
|
|
|
|
/*
|
|
* Mark that the PG_migrate_skip information should be cleared
|
|
* by kswapd when it goes to sleep. kcompactd does not set the
|
|
* flag itself as the decision to be clear should be directly
|
|
* based on an allocation request.
|
|
*/
|
|
if (cc->direct_compaction)
|
|
zone->compact_blockskip_flush = true;
|
|
|
|
if (cc->whole_zone)
|
|
return COMPACT_COMPLETE;
|
|
else
|
|
return COMPACT_PARTIAL_SKIPPED;
|
|
}
|
|
|
|
if (is_via_compact_memory(cc->order))
|
|
return COMPACT_CONTINUE;
|
|
|
|
/* Compaction run is not finished if the watermark is not met */
|
|
watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK];
|
|
|
|
if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
|
|
cc->alloc_flags))
|
|
return COMPACT_CONTINUE;
|
|
|
|
/* Direct compactor: Is a suitable page free? */
|
|
for (order = cc->order; order < MAX_ORDER; order++) {
|
|
struct free_area *area = &zone->free_area[order];
|
|
bool can_steal;
|
|
|
|
/* Job done if page is free of the right migratetype */
|
|
if (!list_empty(&area->free_list[migratetype]))
|
|
return COMPACT_SUCCESS;
|
|
|
|
#ifdef CONFIG_CMA
|
|
/* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
|
|
if (migratetype == MIGRATE_MOVABLE &&
|
|
!list_empty(&area->free_list[MIGRATE_CMA]))
|
|
return COMPACT_SUCCESS;
|
|
#endif
|
|
/*
|
|
* Job done if allocation would steal freepages from
|
|
* other migratetype buddy lists.
|
|
*/
|
|
if (find_suitable_fallback(area, order, migratetype,
|
|
true, &can_steal) != -1)
|
|
return COMPACT_SUCCESS;
|
|
}
|
|
|
|
return COMPACT_NO_SUITABLE_PAGE;
|
|
}
|
|
|
|
static enum compact_result compact_finished(struct zone *zone,
|
|
struct compact_control *cc,
|
|
const int migratetype)
|
|
{
|
|
int ret;
|
|
|
|
ret = __compact_finished(zone, cc, migratetype);
|
|
trace_mm_compaction_finished(zone, cc->order, ret);
|
|
if (ret == COMPACT_NO_SUITABLE_PAGE)
|
|
ret = COMPACT_CONTINUE;
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* compaction_suitable: Is this suitable to run compaction on this zone now?
|
|
* Returns
|
|
* COMPACT_SKIPPED - If there are too few free pages for compaction
|
|
* COMPACT_SUCCESS - If the allocation would succeed without compaction
|
|
* COMPACT_CONTINUE - If compaction should run now
|
|
*/
|
|
static enum compact_result __compaction_suitable(struct zone *zone, int order,
|
|
unsigned int alloc_flags,
|
|
int classzone_idx,
|
|
unsigned long wmark_target)
|
|
{
|
|
unsigned long watermark;
|
|
|
|
if (is_via_compact_memory(order))
|
|
return COMPACT_CONTINUE;
|
|
|
|
watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
|
|
/*
|
|
* If watermarks for high-order allocation are already met, there
|
|
* should be no need for compaction at all.
|
|
*/
|
|
if (zone_watermark_ok(zone, order, watermark, classzone_idx,
|
|
alloc_flags))
|
|
return COMPACT_SUCCESS;
|
|
|
|
/*
|
|
* Watermarks for order-0 must be met for compaction to be able to
|
|
* isolate free pages for migration targets. This means that the
|
|
* watermark and alloc_flags have to match, or be more pessimistic than
|
|
* the check in __isolate_free_page(). We don't use the direct
|
|
* compactor's alloc_flags, as they are not relevant for freepage
|
|
* isolation. We however do use the direct compactor's classzone_idx to
|
|
* skip over zones where lowmem reserves would prevent allocation even
|
|
* if compaction succeeds.
|
|
* For costly orders, we require low watermark instead of min for
|
|
* compaction to proceed to increase its chances.
|
|
* ALLOC_CMA is used, as pages in CMA pageblocks are considered
|
|
* suitable migration targets
|
|
*/
|
|
watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
|
|
low_wmark_pages(zone) : min_wmark_pages(zone);
|
|
watermark += compact_gap(order);
|
|
if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
|
|
ALLOC_CMA, wmark_target))
|
|
return COMPACT_SKIPPED;
|
|
|
|
return COMPACT_CONTINUE;
|
|
}
|
|
|
|
enum compact_result compaction_suitable(struct zone *zone, int order,
|
|
unsigned int alloc_flags,
|
|
int classzone_idx)
|
|
{
|
|
enum compact_result ret;
|
|
int fragindex;
|
|
|
|
ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx,
|
|
zone_page_state(zone, NR_FREE_PAGES));
|
|
/*
|
|
* fragmentation index determines if allocation failures are due to
|
|
* low memory or external fragmentation
|
|
*
|
|
* index of -1000 would imply allocations might succeed depending on
|
|
* watermarks, but we already failed the high-order watermark check
|
|
* index towards 0 implies failure is due to lack of memory
|
|
* index towards 1000 implies failure is due to fragmentation
|
|
*
|
|
* Only compact if a failure would be due to fragmentation. Also
|
|
* ignore fragindex for non-costly orders where the alternative to
|
|
* a successful reclaim/compaction is OOM. Fragindex and the
|
|
* vm.extfrag_threshold sysctl is meant as a heuristic to prevent
|
|
* excessive compaction for costly orders, but it should not be at the
|
|
* expense of system stability.
|
|
*/
|
|
if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
|
|
fragindex = fragmentation_index(zone, order);
|
|
if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
|
|
ret = COMPACT_NOT_SUITABLE_ZONE;
|
|
}
|
|
|
|
trace_mm_compaction_suitable(zone, order, ret);
|
|
if (ret == COMPACT_NOT_SUITABLE_ZONE)
|
|
ret = COMPACT_SKIPPED;
|
|
|
|
return ret;
|
|
}
|
|
|
|
bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
|
|
int alloc_flags)
|
|
{
|
|
struct zone *zone;
|
|
struct zoneref *z;
|
|
|
|
/*
|
|
* Make sure at least one zone would pass __compaction_suitable if we continue
|
|
* retrying the reclaim.
|
|
*/
|
|
for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
|
|
ac->nodemask) {
|
|
unsigned long available;
|
|
enum compact_result compact_result;
|
|
|
|
/*
|
|
* Do not consider all the reclaimable memory because we do not
|
|
* want to trash just for a single high order allocation which
|
|
* is even not guaranteed to appear even if __compaction_suitable
|
|
* is happy about the watermark check.
|
|
*/
|
|
available = zone_reclaimable_pages(zone) / order;
|
|
available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
|
|
compact_result = __compaction_suitable(zone, order, alloc_flags,
|
|
ac_classzone_idx(ac), available);
|
|
if (compact_result != COMPACT_SKIPPED)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc)
|
|
{
|
|
enum compact_result ret;
|
|
unsigned long start_pfn = zone->zone_start_pfn;
|
|
unsigned long end_pfn = zone_end_pfn(zone);
|
|
const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
|
|
const bool sync = cc->mode != MIGRATE_ASYNC;
|
|
|
|
ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
|
|
cc->classzone_idx);
|
|
/* Compaction is likely to fail */
|
|
if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
|
|
return ret;
|
|
|
|
/* huh, compaction_suitable is returning something unexpected */
|
|
VM_BUG_ON(ret != COMPACT_CONTINUE);
|
|
|
|
/*
|
|
* Clear pageblock skip if there were failures recently and compaction
|
|
* is about to be retried after being deferred.
|
|
*/
|
|
if (compaction_restarting(zone, cc->order))
|
|
__reset_isolation_suitable(zone);
|
|
|
|
/*
|
|
* Setup to move all movable pages to the end of the zone. Used cached
|
|
* information on where the scanners should start (unless we explicitly
|
|
* want to compact the whole zone), but check that it is initialised
|
|
* by ensuring the values are within zone boundaries.
|
|
*/
|
|
if (cc->whole_zone) {
|
|
cc->migrate_pfn = start_pfn;
|
|
cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
|
|
} else {
|
|
cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
|
|
cc->free_pfn = zone->compact_cached_free_pfn;
|
|
if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
|
|
cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
|
|
zone->compact_cached_free_pfn = cc->free_pfn;
|
|
}
|
|
if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
|
|
cc->migrate_pfn = start_pfn;
|
|
zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
|
|
zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
|
|
}
|
|
|
|
if (cc->migrate_pfn == start_pfn)
|
|
cc->whole_zone = true;
|
|
}
|
|
|
|
cc->last_migrated_pfn = 0;
|
|
|
|
trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
|
|
cc->free_pfn, end_pfn, sync);
|
|
|
|
migrate_prep_local();
|
|
|
|
while ((ret = compact_finished(zone, cc, migratetype)) ==
|
|
COMPACT_CONTINUE) {
|
|
int err;
|
|
|
|
switch (isolate_migratepages(zone, cc)) {
|
|
case ISOLATE_ABORT:
|
|
ret = COMPACT_CONTENDED;
|
|
putback_movable_pages(&cc->migratepages);
|
|
cc->nr_migratepages = 0;
|
|
goto out;
|
|
case ISOLATE_NONE:
|
|
/*
|
|
* We haven't isolated and migrated anything, but
|
|
* there might still be unflushed migrations from
|
|
* previous cc->order aligned block.
|
|
*/
|
|
goto check_drain;
|
|
case ISOLATE_SUCCESS:
|
|
;
|
|
}
|
|
|
|
err = migrate_pages(&cc->migratepages, compaction_alloc,
|
|
compaction_free, (unsigned long)cc, cc->mode,
|
|
MR_COMPACTION);
|
|
|
|
trace_mm_compaction_migratepages(cc->nr_migratepages, err,
|
|
&cc->migratepages);
|
|
|
|
/* All pages were either migrated or will be released */
|
|
cc->nr_migratepages = 0;
|
|
if (err) {
|
|
putback_movable_pages(&cc->migratepages);
|
|
/*
|
|
* migrate_pages() may return -ENOMEM when scanners meet
|
|
* and we want compact_finished() to detect it
|
|
*/
|
|
if (err == -ENOMEM && !compact_scanners_met(cc)) {
|
|
ret = COMPACT_CONTENDED;
|
|
goto out;
|
|
}
|
|
/*
|
|
* We failed to migrate at least one page in the current
|
|
* order-aligned block, so skip the rest of it.
|
|
*/
|
|
if (cc->direct_compaction &&
|
|
(cc->mode == MIGRATE_ASYNC)) {
|
|
cc->migrate_pfn = block_end_pfn(
|
|
cc->migrate_pfn - 1, cc->order);
|
|
/* Draining pcplists is useless in this case */
|
|
cc->last_migrated_pfn = 0;
|
|
|
|
}
|
|
}
|
|
|
|
check_drain:
|
|
/*
|
|
* Has the migration scanner moved away from the previous
|
|
* cc->order aligned block where we migrated from? If yes,
|
|
* flush the pages that were freed, so that they can merge and
|
|
* compact_finished() can detect immediately if allocation
|
|
* would succeed.
|
|
*/
|
|
if (cc->order > 0 && cc->last_migrated_pfn) {
|
|
int cpu;
|
|
unsigned long current_block_start =
|
|
block_start_pfn(cc->migrate_pfn, cc->order);
|
|
|
|
if (cc->last_migrated_pfn < current_block_start) {
|
|
cpu = get_cpu();
|
|
lru_add_drain_cpu(cpu);
|
|
drain_local_pages(zone);
|
|
put_cpu();
|
|
/* No more flushing until we migrate again */
|
|
cc->last_migrated_pfn = 0;
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
out:
|
|
/*
|
|
* Release free pages and update where the free scanner should restart,
|
|
* so we don't leave any returned pages behind in the next attempt.
|
|
*/
|
|
if (cc->nr_freepages > 0) {
|
|
unsigned long free_pfn = release_freepages(&cc->freepages);
|
|
|
|
cc->nr_freepages = 0;
|
|
VM_BUG_ON(free_pfn == 0);
|
|
/* The cached pfn is always the first in a pageblock */
|
|
free_pfn = pageblock_start_pfn(free_pfn);
|
|
/*
|
|
* Only go back, not forward. The cached pfn might have been
|
|
* already reset to zone end in compact_finished()
|
|
*/
|
|
if (free_pfn > zone->compact_cached_free_pfn)
|
|
zone->compact_cached_free_pfn = free_pfn;
|
|
}
|
|
|
|
trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
|
|
cc->free_pfn, end_pfn, sync, ret);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static enum compact_result compact_zone_order(struct zone *zone, int order,
|
|
gfp_t gfp_mask, enum compact_priority prio,
|
|
unsigned int alloc_flags, int classzone_idx)
|
|
{
|
|
enum compact_result ret;
|
|
struct compact_control cc = {
|
|
.nr_freepages = 0,
|
|
.nr_migratepages = 0,
|
|
.order = order,
|
|
.gfp_mask = gfp_mask,
|
|
.zone = zone,
|
|
.mode = (prio == COMPACT_PRIO_ASYNC) ?
|
|
MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
|
|
.alloc_flags = alloc_flags,
|
|
.classzone_idx = classzone_idx,
|
|
.direct_compaction = true,
|
|
.whole_zone = (prio == MIN_COMPACT_PRIORITY),
|
|
.ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
|
|
.ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
|
|
};
|
|
INIT_LIST_HEAD(&cc.freepages);
|
|
INIT_LIST_HEAD(&cc.migratepages);
|
|
|
|
ret = compact_zone(zone, &cc);
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
|
|
return ret;
|
|
}
|
|
|
|
int sysctl_extfrag_threshold = 500;
|
|
|
|
/**
|
|
* try_to_compact_pages - Direct compact to satisfy a high-order allocation
|
|
* @gfp_mask: The GFP mask of the current allocation
|
|
* @order: The order of the current allocation
|
|
* @alloc_flags: The allocation flags of the current allocation
|
|
* @ac: The context of current allocation
|
|
* @mode: The migration mode for async, sync light, or sync migration
|
|
*
|
|
* This is the main entry point for direct page compaction.
|
|
*/
|
|
enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
|
|
unsigned int alloc_flags, const struct alloc_context *ac,
|
|
enum compact_priority prio)
|
|
{
|
|
int may_perform_io = gfp_mask & __GFP_IO;
|
|
struct zoneref *z;
|
|
struct zone *zone;
|
|
enum compact_result rc = COMPACT_SKIPPED;
|
|
|
|
/*
|
|
* Check if the GFP flags allow compaction - GFP_NOIO is really
|
|
* tricky context because the migration might require IO
|
|
*/
|
|
if (!may_perform_io)
|
|
return COMPACT_SKIPPED;
|
|
|
|
trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
|
|
|
|
/* Compact each zone in the list */
|
|
for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
|
|
ac->nodemask) {
|
|
enum compact_result status;
|
|
|
|
if (prio > MIN_COMPACT_PRIORITY
|
|
&& compaction_deferred(zone, order)) {
|
|
rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
|
|
continue;
|
|
}
|
|
|
|
status = compact_zone_order(zone, order, gfp_mask, prio,
|
|
alloc_flags, ac_classzone_idx(ac));
|
|
rc = max(status, rc);
|
|
|
|
/* The allocation should succeed, stop compacting */
|
|
if (status == COMPACT_SUCCESS) {
|
|
/*
|
|
* We think the allocation will succeed in this zone,
|
|
* but it is not certain, hence the false. The caller
|
|
* will repeat this with true if allocation indeed
|
|
* succeeds in this zone.
|
|
*/
|
|
compaction_defer_reset(zone, order, false);
|
|
|
|
break;
|
|
}
|
|
|
|
if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
|
|
status == COMPACT_PARTIAL_SKIPPED))
|
|
/*
|
|
* We think that allocation won't succeed in this zone
|
|
* so we defer compaction there. If it ends up
|
|
* succeeding after all, it will be reset.
|
|
*/
|
|
defer_compaction(zone, order);
|
|
|
|
/*
|
|
* We might have stopped compacting due to need_resched() in
|
|
* async compaction, or due to a fatal signal detected. In that
|
|
* case do not try further zones
|
|
*/
|
|
if ((prio == COMPACT_PRIO_ASYNC && need_resched())
|
|
|| fatal_signal_pending(current))
|
|
break;
|
|
}
|
|
|
|
return rc;
|
|
}
|
|
|
|
|
|
/* Compact all zones within a node */
|
|
static void compact_node(int nid)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
int zoneid;
|
|
struct zone *zone;
|
|
struct compact_control cc = {
|
|
.order = -1,
|
|
.mode = MIGRATE_SYNC,
|
|
.ignore_skip_hint = true,
|
|
.whole_zone = true,
|
|
.gfp_mask = GFP_KERNEL,
|
|
};
|
|
|
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
|
|
|
|
zone = &pgdat->node_zones[zoneid];
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
cc.nr_freepages = 0;
|
|
cc.nr_migratepages = 0;
|
|
cc.zone = zone;
|
|
INIT_LIST_HEAD(&cc.freepages);
|
|
INIT_LIST_HEAD(&cc.migratepages);
|
|
|
|
compact_zone(zone, &cc);
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
}
|
|
}
|
|
|
|
/* Compact all nodes in the system */
|
|
static void compact_nodes(void)
|
|
{
|
|
int nid;
|
|
|
|
/* Flush pending updates to the LRU lists */
|
|
lru_add_drain_all();
|
|
|
|
for_each_online_node(nid)
|
|
compact_node(nid);
|
|
}
|
|
|
|
/* The written value is actually unused, all memory is compacted */
|
|
int sysctl_compact_memory;
|
|
|
|
/*
|
|
* This is the entry point for compacting all nodes via
|
|
* /proc/sys/vm/compact_memory
|
|
*/
|
|
int sysctl_compaction_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
if (write)
|
|
compact_nodes();
|
|
|
|
return 0;
|
|
}
|
|
|
|
int sysctl_extfrag_handler(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *length, loff_t *ppos)
|
|
{
|
|
proc_dointvec_minmax(table, write, buffer, length, ppos);
|
|
|
|
return 0;
|
|
}
|
|
|
|
#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
|
|
static ssize_t sysfs_compact_node(struct device *dev,
|
|
struct device_attribute *attr,
|
|
const char *buf, size_t count)
|
|
{
|
|
int nid = dev->id;
|
|
|
|
if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
|
|
/* Flush pending updates to the LRU lists */
|
|
lru_add_drain_all();
|
|
|
|
compact_node(nid);
|
|
}
|
|
|
|
return count;
|
|
}
|
|
static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
|
|
|
|
int compaction_register_node(struct node *node)
|
|
{
|
|
return device_create_file(&node->dev, &dev_attr_compact);
|
|
}
|
|
|
|
void compaction_unregister_node(struct node *node)
|
|
{
|
|
return device_remove_file(&node->dev, &dev_attr_compact);
|
|
}
|
|
#endif /* CONFIG_SYSFS && CONFIG_NUMA */
|
|
|
|
static inline bool kcompactd_work_requested(pg_data_t *pgdat)
|
|
{
|
|
return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
|
|
}
|
|
|
|
static bool kcompactd_node_suitable(pg_data_t *pgdat)
|
|
{
|
|
int zoneid;
|
|
struct zone *zone;
|
|
enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
|
|
|
|
for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
|
|
zone = &pgdat->node_zones[zoneid];
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
|
|
classzone_idx) == COMPACT_CONTINUE)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static void kcompactd_do_work(pg_data_t *pgdat)
|
|
{
|
|
/*
|
|
* With no special task, compact all zones so that a page of requested
|
|
* order is allocatable.
|
|
*/
|
|
int zoneid;
|
|
struct zone *zone;
|
|
struct compact_control cc = {
|
|
.order = pgdat->kcompactd_max_order,
|
|
.classzone_idx = pgdat->kcompactd_classzone_idx,
|
|
.mode = MIGRATE_SYNC_LIGHT,
|
|
.ignore_skip_hint = true,
|
|
.gfp_mask = GFP_KERNEL,
|
|
|
|
};
|
|
trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
|
|
cc.classzone_idx);
|
|
count_vm_event(KCOMPACTD_WAKE);
|
|
|
|
for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
|
|
int status;
|
|
|
|
zone = &pgdat->node_zones[zoneid];
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (compaction_deferred(zone, cc.order))
|
|
continue;
|
|
|
|
if (compaction_suitable(zone, cc.order, 0, zoneid) !=
|
|
COMPACT_CONTINUE)
|
|
continue;
|
|
|
|
cc.nr_freepages = 0;
|
|
cc.nr_migratepages = 0;
|
|
cc.zone = zone;
|
|
INIT_LIST_HEAD(&cc.freepages);
|
|
INIT_LIST_HEAD(&cc.migratepages);
|
|
|
|
if (kthread_should_stop())
|
|
return;
|
|
status = compact_zone(zone, &cc);
|
|
|
|
if (status == COMPACT_SUCCESS) {
|
|
compaction_defer_reset(zone, cc.order, false);
|
|
} else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
|
|
/*
|
|
* We use sync migration mode here, so we defer like
|
|
* sync direct compaction does.
|
|
*/
|
|
defer_compaction(zone, cc.order);
|
|
}
|
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages));
|
|
VM_BUG_ON(!list_empty(&cc.migratepages));
|
|
}
|
|
|
|
/*
|
|
* Regardless of success, we are done until woken up next. But remember
|
|
* the requested order/classzone_idx in case it was higher/tighter than
|
|
* our current ones
|
|
*/
|
|
if (pgdat->kcompactd_max_order <= cc.order)
|
|
pgdat->kcompactd_max_order = 0;
|
|
if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx)
|
|
pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
|
|
}
|
|
|
|
void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
|
|
{
|
|
if (!order)
|
|
return;
|
|
|
|
if (pgdat->kcompactd_max_order < order)
|
|
pgdat->kcompactd_max_order = order;
|
|
|
|
if (pgdat->kcompactd_classzone_idx > classzone_idx)
|
|
pgdat->kcompactd_classzone_idx = classzone_idx;
|
|
|
|
if (!waitqueue_active(&pgdat->kcompactd_wait))
|
|
return;
|
|
|
|
if (!kcompactd_node_suitable(pgdat))
|
|
return;
|
|
|
|
trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
|
|
classzone_idx);
|
|
wake_up_interruptible(&pgdat->kcompactd_wait);
|
|
}
|
|
|
|
/*
|
|
* The background compaction daemon, started as a kernel thread
|
|
* from the init process.
|
|
*/
|
|
static int kcompactd(void *p)
|
|
{
|
|
pg_data_t *pgdat = (pg_data_t*)p;
|
|
struct task_struct *tsk = current;
|
|
|
|
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
|
|
|
|
if (!cpumask_empty(cpumask))
|
|
set_cpus_allowed_ptr(tsk, cpumask);
|
|
|
|
set_freezable();
|
|
|
|
pgdat->kcompactd_max_order = 0;
|
|
pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1;
|
|
|
|
while (!kthread_should_stop()) {
|
|
trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
|
|
wait_event_freezable(pgdat->kcompactd_wait,
|
|
kcompactd_work_requested(pgdat));
|
|
|
|
kcompactd_do_work(pgdat);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This kcompactd start function will be called by init and node-hot-add.
|
|
* On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
|
|
*/
|
|
int kcompactd_run(int nid)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
int ret = 0;
|
|
|
|
if (pgdat->kcompactd)
|
|
return 0;
|
|
|
|
pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
|
|
if (IS_ERR(pgdat->kcompactd)) {
|
|
pr_err("Failed to start kcompactd on node %d\n", nid);
|
|
ret = PTR_ERR(pgdat->kcompactd);
|
|
pgdat->kcompactd = NULL;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Called by memory hotplug when all memory in a node is offlined. Caller must
|
|
* hold mem_hotplug_begin/end().
|
|
*/
|
|
void kcompactd_stop(int nid)
|
|
{
|
|
struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
|
|
|
|
if (kcompactd) {
|
|
kthread_stop(kcompactd);
|
|
NODE_DATA(nid)->kcompactd = NULL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* It's optimal to keep kcompactd on the same CPUs as their memory, but
|
|
* not required for correctness. So if the last cpu in a node goes
|
|
* away, we get changed to run anywhere: as the first one comes back,
|
|
* restore their cpu bindings.
|
|
*/
|
|
static int kcompactd_cpu_online(unsigned int cpu)
|
|
{
|
|
int nid;
|
|
|
|
for_each_node_state(nid, N_MEMORY) {
|
|
pg_data_t *pgdat = NODE_DATA(nid);
|
|
const struct cpumask *mask;
|
|
|
|
mask = cpumask_of_node(pgdat->node_id);
|
|
|
|
if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
|
|
/* One of our CPUs online: restore mask */
|
|
set_cpus_allowed_ptr(pgdat->kcompactd, mask);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static int __init kcompactd_init(void)
|
|
{
|
|
int nid;
|
|
int ret;
|
|
|
|
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
|
|
"mm/compaction:online",
|
|
kcompactd_cpu_online, NULL);
|
|
if (ret < 0) {
|
|
pr_err("kcompactd: failed to register hotplug callbacks.\n");
|
|
return ret;
|
|
}
|
|
|
|
for_each_node_state(nid, N_MEMORY)
|
|
kcompactd_run(nid);
|
|
return 0;
|
|
}
|
|
subsys_initcall(kcompactd_init)
|
|
|
|
#endif /* CONFIG_COMPACTION */
|