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59 Commits

Author SHA1 Message Date
Mel Gorman 3cc668f4e3 mm: compaction: move fatal signal check out of compact_checklock_irqsave 
Commit c67fe3752a ("mm: compaction: Abort async compaction if locks
are contended or taking too long") addressed a lock contention problem
in compaction by introducing compact_checklock_irqsave() that effecively
aborting async compaction in the event of compaction.

To preserve existing behaviour it also moved a fatal_signal_pending()
check into compact_checklock_irqsave() but that is very misleading.  It
"hides" the check within a locking function but has nothing to do with
locking as such.  It just happens to work in a desirable fashion.

This patch moves the fatal_signal_pending() check to
isolate_migratepages_range() where it belongs.  Arguably the same check
should also happen when isolating pages for freeing but it's overkill.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:48 +09:00
Shaohua Li e64c5237cf mm: compaction: abort compaction loop if lock is contended or run too long 
isolate_migratepages_range() might isolate no pages if for example when
zone->lru_lock is contended and running asynchronous compaction. In this
case, we should abort compaction, otherwise, compact_zone will run a
useless loop and make zone->lru_lock is even contended.

An additional check is added to ensure that cc.migratepages and
cc.freepages get properly drained whan compaction is aborted.

[minchan@kernel.org: Putback pages isolated for migration if aborting]
[akpm@linux-foundation.org: compact_zone_order requires non-NULL arg contended]
[akpm@linux-foundation.org: make compact_zone_order() require non-NULL arg `contended']
[minchan@kernel.org: Putback pages isolated for migration if aborting]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:48 +09:00
Bartlomiej Zolnierkiewicz d95ea5d18e cma: fix watermark checking 
* Add ALLOC_CMA alloc flag and pass it to [__]zone_watermark_ok()
  (from Minchan Kim).

* During watermark check decrease available free pages number by
  free CMA pages number if necessary (unmovable allocations cannot
  use pages from CMA areas).

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:45 +09:00
Mel Gorman 1fb3f8ca0e mm: compaction: capture a suitable high-order page immediately when it is made available 
While compaction is migrating pages to free up large contiguous blocks
for allocation it races with other allocation requests that may steal
these blocks or break them up.  This patch alters direct compaction to
capture a suitable free page as soon as it becomes available to reduce
this race.  It uses similar logic to split_free_page() to ensure that
watermarks are still obeyed.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:21 +09:00
Mel Gorman 4ffb6335da mm: compaction: update comment in try_to_compact_pages 
Allocation success rates have been far lower since 3.4 due to commit
fe2c2a1066 ("vmscan: reclaim at order 0 when compaction is enabled").
This commit was introduced for good reasons and it was known in advance
that the success rates would suffer but it was justified on the grounds
that the high allocation success rates were achieved by aggressive
reclaim.  Success rates are expected to suffer even more in 3.6 due to
commit 7db8889ab0 ("mm: have order > 0 compaction start off where it
left") which testing has shown to severely reduce allocation success
rates under load - to 0% in one case.

This series aims to improve the allocation success rates without
regressing the benefits of commit fe2c2a1066.  The series is based on
latest mmotm and takes into account the __GFP_NO_KSWAPD flag is going
away.

Patch 1 updates a stale comment seeing as I was in the general area.

Patch 2 updates reclaim/compaction to reclaim pages scaled on the number
	of recent failures.

Patch 3 captures suitable high-order pages freed by compaction to reduce
	races with parallel allocation requests.

Patch 4 fixes the upstream commit [7db8889a: mm: have order > 0 compaction
	start off where it left] to enable compaction again

Patch 5 identifies when compacion is taking too long due to contention
	and aborts.

STRESS-HIGHALLOC
		 3.6-rc1-akpm	  full-series
Pass 1          36.00 ( 0.00%)    51.00 (15.00%)
Pass 2          42.00 ( 0.00%)    63.00 (21.00%)
while Rested    86.00 ( 0.00%)    86.00 ( 0.00%)

From

  http://www.csn.ul.ie/~mel/postings/mmtests-20120424/global-dhp__stress-highalloc-performance-ext3/hydra/comparison.html

I know that the allocation success rates in 3.3.6 was 78% in comparison
to 36% in in the current akpm tree.  With the full series applied, the
success rates are up to around 51% with some variability in the results.
This is not as high a success rate but it does not reclaim excessively
which is a key point.

MMTests Statistics: vmstat
Page Ins                                     3050912     3078892
Page Outs                                    8033528     8039096
Swap Ins                                           0           0
Swap Outs                                          0           0

Note that swap in/out rates remain at 0. In 3.3.6 with 78% success rates
there were 71881 pages swapped out.

Direct pages scanned                           70942      122976
Kswapd pages scanned                         1366300     1520122
Kswapd pages reclaimed                       1366214     1484629
Direct pages reclaimed                         70936      105716
Kswapd efficiency                                99%         97%
Kswapd velocity                             1072.550    1182.615
Direct efficiency                                99%         85%
Direct velocity                               55.690      95.672

The kswapd velocity changes very little as expected.  kswapd velocity is
around the 1000 pages/sec mark where as in kernel 3.3.6 with the high
allocation success rates it was 8140 pages/second.  Direct velocity is
higher as a result of patch 2 of the series but this is expected and is
acceptable.  The direct reclaim and kswapd velocities change very little.

If these get accepted for merging then there is a difficulty in how they
should be handled.  7db8889a ("mm: have order > 0 compaction start off
where it left") is broken but it is already in 3.6-rc1 and needs to be
fixed.  However, if just patch 4 from this series is applied then Jim
Schutt's workload is known to break again as his workload also requires
patch 5.  While it would be preferred to have all these patches in 3.6 to
improve compaction in general, it would at least be acceptable if just
patches 4 and 5 were merged to 3.6 to fix a known problem without breaking
compaction completely.  On the face of it, that would force
__GFP_NO_KSWAPD patches to be merged at the same time but I can do a
version of this series with __GFP_NO_KSWAPD change reverted and then
rebase it on top of this series.  That might be best overall because I
note that the __GFP_NO_KSWAPD patch should have removed
deferred_compaction from page_alloc.c but it didn't but fixing that causes
collisions with this series.

This patch:

The comment about order applied when the check was order >
PAGE_ALLOC_COSTLY_ORDER which has not been the case since c5a73c3d ("thp:
use compaction for all allocation orders").  Fixing the comment while I'm
in the general area.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-10-09 16:22:20 +09:00
Mel Gorman c67fe3752a mm: compaction: Abort async compaction if locks are contended or taking too long 
Jim Schutt reported a problem that pointed at compaction contending
heavily on locks.  The workload is straight-forward and in his own words;

	The systems in question have 24 SAS drives spread across 3 HBAs,
	running 24 Ceph OSD instances, one per drive.  FWIW these servers
	are dual-socket Intel 5675 Xeons w/48 GB memory.  I've got ~160
	Ceph Linux clients doing dd simultaneously to a Ceph file system
	backed by 12 of these servers.

Early in the test everything looks fine

  procs -------------------memory------------------ ---swap-- -----io---- --system-- -----cpu-------
   r  b       swpd       free       buff      cache   si   so    bi    bo   in   cs  us sy  id wa st
  31 15          0     287216        576   38606628    0    0     2  1158    2   14   1  3  95  0  0
  27 15          0     225288        576   38583384    0    0    18 2222016 203357 134876  11 56  17 15  0
  28 17          0     219256        576   38544736    0    0    11 2305932 203141 146296  11 49  23 17  0
   6 18          0     215596        576   38552872    0    0     7 2363207 215264 166502  12 45  22 20  0
  22 18          0     226984        576   38596404    0    0     3 2445741 223114 179527  12 43  23 22  0

and then it goes to pot

  procs -------------------memory------------------ ---swap-- -----io---- --system-- -----cpu-------
   r  b       swpd       free       buff      cache   si   so    bi    bo   in   cs  us sy  id wa st
  163  8          0     464308        576   36791368    0    0    11 22210  866  536   3 13  79  4  0
  207 14          0     917752        576   36181928    0    0   712 1345376 134598 47367   7 90   1  2  0
  123 12          0     685516        576   36296148    0    0   429 1386615 158494 60077   8 84   5  3  0
  123 12          0     598572        576   36333728    0    0  1107 1233281 147542 62351   7 84   5  4  0
  622  7          0     660768        576   36118264    0    0   557 1345548 151394 59353   7 85   4  3  0
  223 11          0     283960        576   36463868    0    0    46 1107160 121846 33006   6 93   1  1  0

Note that system CPU usage is very high blocks being written out has
dropped by 42%. He analysed this with perf and found

  perf record -g -a sleep 10
  perf report --sort symbol --call-graph fractal,5
    34.63%  [k] _raw_spin_lock_irqsave
            |
            |--97.30%-- isolate_freepages
            |          compaction_alloc
            |          unmap_and_move
            |          migrate_pages
            |          compact_zone
            |          compact_zone_order
            |          try_to_compact_pages
            |          __alloc_pages_direct_compact
            |          __alloc_pages_slowpath
            |          __alloc_pages_nodemask
            |          alloc_pages_vma
            |          do_huge_pmd_anonymous_page
            |          handle_mm_fault
            |          do_page_fault
            |          page_fault
            |          |
            |          |--87.39%-- skb_copy_datagram_iovec
            |          |          tcp_recvmsg
            |          |          inet_recvmsg
            |          |          sock_recvmsg
            |          |          sys_recvfrom
            |          |          system_call
            |          |          __recv
            |          |          |
            |          |           --100.00%-- (nil)
            |          |
            |           --12.61%-- memcpy
             --2.70%-- [...]

There was other data but primarily it is all showing that compaction is
contended heavily on the zone->lock and zone->lru_lock.

commit [b2eef8c0: mm: compaction: minimise the time IRQs are disabled
while isolating pages for migration] noted that it was possible for
migration to hold the lru_lock for an excessive amount of time. Very
broadly speaking this patch expands the concept.

This patch introduces compact_checklock_irqsave() to check if a lock
is contended or the process needs to be scheduled. If either condition
is true then async compaction is aborted and the caller is informed.
The page allocator will fail a THP allocation if compaction failed due
to contention. This patch also introduces compact_trylock_irqsave()
which will acquire the lock only if it is not contended and the process
does not need to schedule.

Reported-by: Jim Schutt <jaschut@sandia.gov>
Tested-by: Jim Schutt <jaschut@sandia.gov>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-08-21 16:45:03 -07:00
Mel Gorman de74f1cc3b mm: have order > 0 compaction start near a pageblock with free pages 
Commit 7db8889ab0 ("mm: have order > 0 compaction start off where it
left") introduced a caching mechanism to reduce the amount work the free
page scanner does in compaction.  However, it has a problem.  Consider
two process simultaneously scanning free pages

					    			C
	Process A		M     S     			F
			|---------------------------------------|
	Process B		M 	FS

	C is zone->compact_cached_free_pfn
	S is cc->start_pfree_pfn
	M is cc->migrate_pfn
	F is cc->free_pfn

In this diagram, Process A has just reached its migrate scanner, wrapped
around and updated compact_cached_free_pfn accordingly.

Simultaneously, Process B finishes isolating in a block and updates
compact_cached_free_pfn again to the location of its free scanner.

Process A moves to "end_of_zone - one_pageblock" and runs this check

                if (cc->order > 0 && (!cc->wrapped ||
                                      zone->compact_cached_free_pfn >
                                      cc->start_free_pfn))
                        pfn = min(pfn, zone->compact_cached_free_pfn);

compact_cached_free_pfn is above where it started so the free scanner
skips almost the entire space it should have scanned.  When there are
multiple processes compacting it can end in a situation where the entire
zone is not being scanned at all.  Further, it is possible for two
processes to ping-pong update to compact_cached_free_pfn which is just
random.

Overall, the end result wrecks allocation success rates.

There is not an obvious way around this problem without introducing new
locking and state so this patch takes a different approach.

First, it gets rid of the skip logic because it's not clear that it
matters if two free scanners happen to be in the same block but with
racing updates it's too easy for it to skip over blocks it should not.

Second, it updates compact_cached_free_pfn in a more limited set of
circumstances.

If a scanner has wrapped, it updates compact_cached_free_pfn to the end
	of the zone. When a wrapped scanner isolates a page, it updates
	compact_cached_free_pfn to point to the highest pageblock it
	can isolate pages from.

If a scanner has not wrapped when it has finished isolated pages it
	checks if compact_cached_free_pfn is pointing to the end of the
	zone. If so, the value is updated to point to the highest
	pageblock that pages were isolated from. This value will not
	be updated again until a free page scanner wraps and resets
	compact_cached_free_pfn.

This is not optimal and it can still race but the compact_cached_free_pfn
will be pointing to or very near a pageblock with free pages.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-08-21 16:45:03 -07:00
Minchan Kim c81758fbe0 mm/compaction.c: fix deferring compaction mistake 
Commit aff622495c ("vmscan: only defer compaction for failed order and
higher") fixed bad deferring policy but made mistake about checking
compact_order_failed in __compact_pgdat().  So it can't update
compact_order_failed with the new order.  This ends up preventing
correct operation of policy deferral.  This patch fixes it.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-08-21 16:45:03 -07:00
Rik van Riel 7db8889ab0 mm: have order > 0 compaction start off where it left 
Order > 0 compaction stops when enough free pages of the correct page
order have been coalesced.  When doing subsequent higher order
allocations, it is possible for compaction to be invoked many times.

However, the compaction code always starts out looking for things to
compact at the start of the zone, and for free pages to compact things to
at the end of the zone.

This can cause quadratic behaviour, with isolate_freepages starting at the
end of the zone each time, even though previous invocations of the
compaction code already filled up all free memory on that end of the zone.

This can cause isolate_freepages to take enormous amounts of CPU with
certain workloads on larger memory systems.

The obvious solution is to have isolate_freepages remember where it left
off last time, and continue at that point the next time it gets invoked
for an order > 0 compaction.  This could cause compaction to fail if
cc->free_pfn and cc->migrate_pfn are close together initially, in that
case we restart from the end of the zone and try once more.

Forced full (order == -1) compactions are left alone.

[akpm@linux-foundation.org: checkpatch fixes]
[akpm@linux-foundation.org: s/laste/last/, use 80 cols]
Signed-off-by: Rik van Riel <riel@redhat.com>
Reported-by: Jim Schutt <jaschut@sandia.gov>
Tested-by: Jim Schutt <jaschut@sandia.gov>
Cc: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-07-31 18:42:43 -07:00
David Rientjes 4bf2bba375 mm, thp: abort compaction if migration page cannot be charged to memcg 
If page migration cannot charge the temporary page to the memcg,
migrate_pages() will return -ENOMEM.  This isn't considered in memory
compaction however, and the loop continues to iterate over all
pageblocks trying to isolate and migrate pages.  If a small number of
very large memcgs happen to be oom, however, these attempts will mostly
be futile leading to an enormous amout of cpu consumption due to the
page migration failures.

This patch will short circuit and fail memory compaction if
migrate_pages() returns -ENOMEM.  COMPACT_PARTIAL is returned in case
some migrations were successful so that the page allocator will retry.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@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>
 2012-07-11 16:04:43 -07:00
Linus Torvalds 68e3e92620 Revert "mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks" 
This reverts commit 5ceb9ce6fe.

That commit seems to be the cause of the mm compation list corruption
issues that Dave Jones reported.  The locking (or rather, absense
there-of) is dubious, as is the use of the 'page' variable once it has
been found to be outside the pageblock range.

So revert it for now, we can re-visit this for 3.6.  If we even need to:
as Minchan Kim says, "The patch wasn't a bug fix and even test workload
was very theoretical".

Reported-and-tested-by: Dave Jones <davej@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-06-03 20:05:57 -07:00
Hugh Dickins fa9add641b mm/memcg: apply add/del_page to lruvec 
Take lruvec further: pass it instead of zone to add_page_to_lru_list() and
del_page_from_lru_list(); and pagevec_lru_move_fn() pass lruvec down to
its target functions.

This cleanup eliminates a swathe of cruft in memcontrol.c, including
mem_cgroup_lru_add_list(), mem_cgroup_lru_del_list() and
mem_cgroup_lru_move_lists() - which never actually touched the lists.

In their place, mem_cgroup_page_lruvec() to decide the lruvec, previously
a side-effect of add, and mem_cgroup_update_lru_size() to maintain the
lru_size stats.

Whilst these are simplifications in their own right, the goal is to bring
the evaluation of lruvec next to the spin_locking of the lrus, in
preparation for a future patch.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-05-29 16:22:28 -07:00
Konstantin Khlebnikov f3fd4a6192 mm: remove lru type checks from __isolate_lru_page() 
After patch "mm: forbid lumpy-reclaim in shrink_active_list()" we can
completely remove anon/file and active/inactive lru type filters from
__isolate_lru_page(), because isolation for 0-order reclaim always
isolates pages from right lru list.  And pages-isolation for lumpy
shrink_inactive_list() or memory-compaction anyway allowed to isolate
pages from all evictable lru lists.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-05-29 16:22:25 -07:00
Bartlomiej Zolnierkiewicz 5ceb9ce6fe mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks 
When MIGRATE_UNMOVABLE pages are freed from MIGRATE_UNMOVABLE type
pageblock (and some MIGRATE_MOVABLE pages are left in it) waiting until an
allocation takes ownership of the block may take too long.  The type of
the pageblock remains unchanged so the pageblock cannot be used as a
migration target during compaction.

Fix it by:

* Adding enum compact_mode (COMPACT_ASYNC_[MOVABLE,UNMOVABLE], and
  COMPACT_SYNC) and then converting sync field in struct compact_control
  to use it.

* Adding nr_pageblocks_skipped field to struct compact_control and
  tracking how many destination pageblocks were of MIGRATE_UNMOVABLE type.
   If COMPACT_ASYNC_MOVABLE mode compaction ran fully in
  try_to_compact_pages() (COMPACT_COMPLETE) it implies that there is not a
  suitable page for allocation.  In this case then check how if there were
  enough MIGRATE_UNMOVABLE pageblocks to try a second pass in
  COMPACT_ASYNC_UNMOVABLE mode.

* Scanning the MIGRATE_UNMOVABLE pageblocks (during COMPACT_SYNC and
  COMPACT_ASYNC_UNMOVABLE compaction modes) and building a count based on
  finding PageBuddy pages, page_count(page) == 0 or PageLRU pages.  If all
  pages within the MIGRATE_UNMOVABLE pageblock are in one of those three
  sets change the whole pageblock type to MIGRATE_MOVABLE.

My particular test case (on a ARM EXYNOS4 device with 512 MiB, which means
131072 standard 4KiB pages in 'Normal' zone) is to:

- allocate 120000 pages for kernel's usage
- free every second page (60000 pages) of memory just allocated
- allocate and use 60000 pages from user space
- free remaining 60000 pages of kernel memory
  (now we have fragmented memory occupied mostly by user space pages)
- try to allocate 100 order-9 (2048 KiB) pages for kernel's usage

The results:
- with compaction disabled I get 11 successful allocations
- with compaction enabled - 14 successful allocations
- with this patch I'm able to get all 100 successful allocations

NOTE: If we can make kswapd aware of order-0 request during compaction, we
can enhance kswapd with changing mode to COMPACT_ASYNC_FULL
(COMPACT_ASYNC_MOVABLE + COMPACT_ASYNC_UNMOVABLE).  Please see the
following thread:

	http://marc.info/?l=linux-mm&m=133552069417068&w=2

[minchan@kernel.org: minor cleanups]
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-05-29 16:22:22 -07:00
Michal Nazarewicz 47118af076 mm: mmzone: MIGRATE_CMA migration type added 
The MIGRATE_CMA migration type has two main characteristics:
(i) only movable pages can be allocated from MIGRATE_CMA
pageblocks and (ii) page allocator will never change migration
type of MIGRATE_CMA pageblocks.

This guarantees (to some degree) that page in a MIGRATE_CMA page
block can always be migrated somewhere else (unless there's no
memory left in the system).

It is designed to be used for allocating big chunks (eg. 10MiB)
of physically contiguous memory.  Once driver requests
contiguous memory, pages from MIGRATE_CMA pageblocks may be
migrated away to create a contiguous block.

To minimise number of migrations, MIGRATE_CMA migration type
is the last type tried when page allocator falls back to other
migration types when requested.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>
 2012-05-21 15:09:32 +02:00
Michal Nazarewicz ff9543fd32 mm: compaction: export some of the functions 
This commit exports some of the functions from compaction.c file
outside of it adding their declaration into internal.h header
file so that other mm related code can use them.

This forced compaction.c to always be compiled (as opposed to being
compiled only if CONFIG_COMPACTION is defined) but as to avoid
introducing code that user did not ask for, part of the compaction.c
is now wrapped in on #ifdef.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>
 2012-05-21 15:09:30 +02:00
Michal Nazarewicz 85aa125f00 mm: compaction: introduce isolate_freepages_range() 
This commit introduces isolate_freepages_range() function which
generalises isolate_freepages_block() so that it can be used on
arbitrary PFN ranges.

isolate_freepages_block() is left with only minor changes.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>
 2012-05-21 15:09:29 +02:00
Michal Nazarewicz 03d44192f6 mm: compaction: introduce map_pages() 
This commit creates a map_pages() function which map pages freed
using split_free_pages().  This merely moves some code from
isolate_freepages() so that it can be reused in other places.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>
 2012-05-21 15:09:28 +02:00
Michal Nazarewicz 2fe86e0004 mm: compaction: introduce isolate_migratepages_range() 
This commit introduces isolate_migratepages_range() function which
extracts functionality from isolate_migratepages() so that it can be
used on arbitrary PFN ranges.

isolate_migratepages() function is implemented as a simple wrapper
around isolate_migratepages_range().

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>
 2012-05-21 15:09:27 +02:00
Dan Carpenter aad6ec3777 mm: compaction: make compact_control order signed 
"order" is -1 when compacting via /proc/sys/vm/compact_memory.  Making
it unsigned causes a bug in __compact_pgdat() when we test:

	if (cc->order < 0 || !compaction_deferred(zone, cc->order))
		compact_zone(zone, cc);

[akpm@linux-foundation.org: make __compact_pgdat()'s comparison match other code sites]
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-03-21 17:54:56 -07:00
Hugh Dickins 8575ec29f6 compact_pgdat: workaround lockdep warning in kswapd 
I get this lockdep warning from swapping load on linux-next, due to
"vmscan: kswapd carefully call compaction".

=================================
[ INFO: inconsistent lock state ]
3.3.0-rc2-next-20120201 #5 Not tainted
---------------------------------
inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
kswapd0/28 [HC0[0]:SC0[0]:HE1:SE1] takes:
 (pcpu_alloc_mutex){+.+.?.}, at: [<ffffffff810d6684>] pcpu_alloc+0x67/0x325
{RECLAIM_FS-ON-W} state was registered at:
  [<ffffffff81099b75>] mark_held_locks+0xd7/0x103
  [<ffffffff8109a13c>] lockdep_trace_alloc+0x85/0x9e
  [<ffffffff810f6bdc>] __kmalloc+0x6c/0x14b
  [<ffffffff810d57fd>] pcpu_mem_zalloc+0x59/0x62
  [<ffffffff810d5d16>] pcpu_extend_area_map+0x26/0xb1
  [<ffffffff810d679f>] pcpu_alloc+0x182/0x325
  [<ffffffff810d694d>] __alloc_percpu+0xb/0xd
  [<ffffffff8142ebfd>] snmp_mib_init+0x1e/0x2e
  [<ffffffff8185cd8d>] ipv4_mib_init_net+0x7a/0x184
  [<ffffffff813dc963>] ops_init.clone.0+0x6b/0x73
  [<ffffffff813dc9cc>] register_pernet_operations+0x61/0xa0
  [<ffffffff813dca8e>] register_pernet_subsys+0x29/0x42
  [<ffffffff8185d044>] inet_init+0x1ad/0x252
  [<ffffffff810002e3>] do_one_initcall+0x7a/0x12f
  [<ffffffff81832bc5>] kernel_init+0x9d/0x11e
  [<ffffffff814e51e4>] kernel_thread_helper+0x4/0x10
irq event stamp: 656613
hardirqs last  enabled at (656613): [<ffffffff814e0ddc>] __mutex_unlock_slowpath+0x104/0x128
hardirqs last disabled at (656612): [<ffffffff814e0d34>] __mutex_unlock_slowpath+0x5c/0x128
softirqs last  enabled at (655568): [<ffffffff8105b4a5>] __do_softirq+0x120/0x136
softirqs last disabled at (654757): [<ffffffff814e52dc>] call_softirq+0x1c/0x30

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(pcpu_alloc_mutex);
  <Interrupt>
    lock(pcpu_alloc_mutex);

 *** DEADLOCK ***

no locks held by kswapd0/28.

stack backtrace:
Pid: 28, comm: kswapd0 Not tainted 3.3.0-rc2-next-20120201 #5
Call Trace:
 [<ffffffff810981f4>] print_usage_bug+0x1bf/0x1d0
 [<ffffffff81096c3e>] ? print_irq_inversion_bug+0x1d9/0x1d9
 [<ffffffff810982c0>] mark_lock_irq+0xbb/0x22e
 [<ffffffff810c5399>] ? free_hot_cold_page+0x13d/0x14f
 [<ffffffff81098684>] mark_lock+0x251/0x331
 [<ffffffff81098893>] mark_irqflags+0x12f/0x141
 [<ffffffff81098e32>] __lock_acquire+0x58d/0x753
 [<ffffffff810d6684>] ? pcpu_alloc+0x67/0x325
 [<ffffffff81099433>] lock_acquire+0x54/0x6a
 [<ffffffff810d6684>] ? pcpu_alloc+0x67/0x325
 [<ffffffff8107a5b8>] ? add_preempt_count+0xa9/0xae
 [<ffffffff814e0a21>] mutex_lock_nested+0x5e/0x315
 [<ffffffff810d6684>] ? pcpu_alloc+0x67/0x325
 [<ffffffff81098f81>] ? __lock_acquire+0x6dc/0x753
 [<ffffffff810c9fb0>] ? __pagevec_release+0x2c/0x2c
 [<ffffffff810d6684>] pcpu_alloc+0x67/0x325
 [<ffffffff810c9fb0>] ? __pagevec_release+0x2c/0x2c
 [<ffffffff810d694d>] __alloc_percpu+0xb/0xd
 [<ffffffff8106c35e>] schedule_on_each_cpu+0x23/0x110
 [<ffffffff810c9fcb>] lru_add_drain_all+0x10/0x12
 [<ffffffff810f126f>] __compact_pgdat+0x20/0x182
 [<ffffffff810f15c2>] compact_pgdat+0x27/0x29
 [<ffffffff810c306b>] ? zone_watermark_ok+0x1a/0x1c
 [<ffffffff810cdf6f>] balance_pgdat+0x732/0x751
 [<ffffffff810ce0ed>] kswapd+0x15f/0x178
 [<ffffffff810cdf8e>] ? balance_pgdat+0x751/0x751
 [<ffffffff8106fd11>] kthread+0x84/0x8c
 [<ffffffff814e51e4>] kernel_thread_helper+0x4/0x10
 [<ffffffff810787ed>] ? finish_task_switch+0x85/0xea
 [<ffffffff814e3861>] ? retint_restore_args+0xe/0xe
 [<ffffffff8106fc8d>] ? __init_kthread_worker+0x56/0x56
 [<ffffffff814e51e0>] ? gs_change+0xb/0xb

The RECLAIM_FS notations indicate that it's doing the GFP_FS checking that
Nick hacked into lockdep a while back: I think we're intended to read that
"<Interrupt>" in the DEADLOCK scenario as "<Direct reclaim>".

I'm hazy, I have not reached any conclusion as to whether it's right to
complain or not; but I believe it's uneasy about kswapd now doing the
mutex_lock(&pcpu_alloc_mutex) which lru_add_drain_all() entails.  Nor have
I reached any conclusion as to whether it's important for kswapd to do
that draining or not.

But so as not to get blocked on this, with lockdep disabled from giving
further reports, here's a patch which removes the lru_add_drain_all() from
kswapd's callpath (and calls it only once from compact_nodes(), instead of
once per node).

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-03-21 17:54:56 -07:00
Rik van Riel aff622495c vmscan: only defer compaction for failed order and higher 
Currently a failed order-9 (transparent hugepage) compaction can lead to
memory compaction being temporarily disabled for a memory zone.  Even if
we only need compaction for an order 2 allocation, eg.  for jumbo frames
networking.

The fix is relatively straightforward: keep track of the highest order at
which compaction is succeeding, and only defer compaction for orders at
which compaction is failing.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-03-21 17:54:56 -07:00
Rik van Riel 7be62de99a vmscan: kswapd carefully call compaction 
With CONFIG_COMPACTION enabled, kswapd does not try to free contiguous
free pages, even when it is woken for a higher order request.

This could be bad for eg.  jumbo frame network allocations, which are done
from interrupt context and cannot compact memory themselves.  Higher than
before allocation failure rates in the network receive path have been
observed in kernels with compaction enabled.

Teach kswapd to defragment the memory zones in a node, but only if
required and compaction is not deferred in a zone.

[akpm@linux-foundation.org: reduce scope of zones_need_compaction]
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-03-21 17:54:56 -07:00
Mel Gorman dc9086004b mm: compaction: check for overlapping nodes during isolation for migration 
When isolating pages for migration, migration starts at the start of a
zone while the free scanner starts at the end of the zone.  Migration
avoids entering a new zone by never going beyond the free scanned.

Unfortunately, in very rare cases nodes can overlap.  When this happens,
migration isolates pages without the LRU lock held, corrupting lists
which will trigger errors in reclaim or during page free such as in the
following oops

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  IP: [<ffffffff810f795c>] free_pcppages_bulk+0xcc/0x450
  PGD 1dda554067 PUD 1e1cb58067 PMD 0
  Oops: 0000 [#1] SMP
  CPU 37
  Pid: 17088, comm: memcg_process_s Tainted: G            X
  RIP: free_pcppages_bulk+0xcc/0x450
  Process memcg_process_s (pid: 17088, threadinfo ffff881c2926e000, task ffff881c2926c0c0)
  Call Trace:
    free_hot_cold_page+0x17e/0x1f0
    __pagevec_free+0x90/0xb0
    release_pages+0x22a/0x260
    pagevec_lru_move_fn+0xf3/0x110
    putback_lru_page+0x66/0xe0
    unmap_and_move+0x156/0x180
    migrate_pages+0x9e/0x1b0
    compact_zone+0x1f3/0x2f0
    compact_zone_order+0xa2/0xe0
    try_to_compact_pages+0xdf/0x110
    __alloc_pages_direct_compact+0xee/0x1c0
    __alloc_pages_slowpath+0x370/0x830
    __alloc_pages_nodemask+0x1b1/0x1c0
    alloc_pages_vma+0x9b/0x160
    do_huge_pmd_anonymous_page+0x160/0x270
    do_page_fault+0x207/0x4c0
    page_fault+0x25/0x30

The "X" in the taint flag means that external modules were loaded but but
is unrelated to the bug triggering.  The real problem was because the PFN
layout looks like this

  Zone PFN ranges:
    DMA      0x00000010 -> 0x00001000
    DMA32    0x00001000 -> 0x00100000
    Normal   0x00100000 -> 0x01e80000
  Movable zone start PFN for each node
  early_node_map[14] active PFN ranges
      0: 0x00000010 -> 0x0000009b
      0: 0x00000100 -> 0x0007a1ec
      0: 0x0007a354 -> 0x0007a379
      0: 0x0007f7ff -> 0x0007f800
      0: 0x00100000 -> 0x00680000
      1: 0x00680000 -> 0x00e80000
      0: 0x00e80000 -> 0x01080000
      1: 0x01080000 -> 0x01280000
      0: 0x01280000 -> 0x01480000
      1: 0x01480000 -> 0x01680000
      0: 0x01680000 -> 0x01880000
      1: 0x01880000 -> 0x01a80000
      0: 0x01a80000 -> 0x01c80000
      1: 0x01c80000 -> 0x01e80000

The fix is straight-forward.  isolate_migratepages() has to make a
similar check to isolate_freepage to ensure that it never isolates pages
from a zone it does not hold the LRU lock for.

This was discovered in a 3.0-based kernel but it affects 3.1.x, 3.2.x
and current mainline.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-02-08 19:03:51 -08:00
Mel Gorman 0bf380bc70 mm: compaction: check pfn_valid when entering a new MAX_ORDER_NR_PAGES block during isolation for migration 
When isolating for migration, migration starts at the start of a zone
which is not necessarily pageblock aligned.  Further, it stops isolating
when COMPACT_CLUSTER_MAX pages are isolated so migrate_pfn is generally
not aligned.  This allows isolate_migratepages() to call pfn_to_page() on
an invalid PFN which can result in a crash.  This was originally reported
against a 3.0-based kernel with the following trace in a crash dump.

PID: 9902   TASK: d47aecd0  CPU: 0   COMMAND: "memcg_process_s"
 #0 [d72d3ad0] crash_kexec at c028cfdb
 #1 [d72d3b24] oops_end at c05c5322
 #2 [d72d3b38] __bad_area_nosemaphore at c0227e60
 #3 [d72d3bec] bad_area at c0227fb6
 #4 [d72d3c00] do_page_fault at c05c72ec
 #5 [d72d3c80] error_code (via page_fault) at c05c47a4
    EAX: 00000000  EBX: 000c0000  ECX: 00000001  EDX: 00000807  EBP: 000c0000
    DS:  007b      ESI: 00000001  ES:  007b      EDI: f3000a80  GS:  6f50
    CS:  0060      EIP: c030b15a  ERR: ffffffff  EFLAGS: 00010002
 #6 [d72d3cb4] isolate_migratepages at c030b15a
 #7 [d72d3d14] zone_watermark_ok at c02d26cb
 #8 [d72d3d2c] compact_zone at c030b8de
 #9 [d72d3d68] compact_zone_order at c030bba1
#10 [d72d3db4] try_to_compact_pages at c030bc84
#11 [d72d3ddc] __alloc_pages_direct_compact at c02d61e7
#12 [d72d3e08] __alloc_pages_slowpath at c02d66c7
#13 [d72d3e78] __alloc_pages_nodemask at c02d6a97
#14 [d72d3eb8] alloc_pages_vma at c030a845
#15 [d72d3ed4] do_huge_pmd_anonymous_page at c03178eb
#16 [d72d3f00] handle_mm_fault at c02f36c6
#17 [d72d3f30] do_page_fault at c05c70ed
#18 [d72d3fb0] error_code (via page_fault) at c05c47a4
    EAX: b71ff000  EBX: 00000001  ECX: 00001600  EDX: 00000431
    DS:  007b      ESI: 08048950  ES:  007b      EDI: bfaa3788
    SS:  007b      ESP: bfaa36e0  EBP: bfaa3828  GS:  6f50
    CS:  0073      EIP: 080487c8  ERR: ffffffff  EFLAGS: 00010202

It was also reported by Herbert van den Bergh against 3.1-based kernel
with the following snippet from the console log.

BUG: unable to handle kernel paging request at 01c00008
IP: [<c0522399>] isolate_migratepages+0x119/0x390
*pdpt = 000000002f7ce001 *pde = 0000000000000000

It is expected that it also affects 3.2.x and current mainline.

The problem is that pfn_valid is only called on the first PFN being
checked and that PFN is not necessarily aligned.  Lets say we have a case
like this

H = MAX_ORDER_NR_PAGES boundary
| = pageblock boundary
m = cc->migrate_pfn
f = cc->free_pfn
o = memory hole

H------|------H------|----m-Hoooooo|ooooooH-f----|------H

The migrate_pfn is just below a memory hole and the free scanner is beyond
the hole.  When isolate_migratepages started, it scans from migrate_pfn to
migrate_pfn+pageblock_nr_pages which is now in a memory hole.  It checks
pfn_valid() on the first PFN but then scans into the hole where there are
not necessarily valid struct pages.

This patch ensures that isolate_migratepages calls pfn_valid when
necessary.

Reported-by: Herbert van den Bergh <herbert.van.den.bergh@oracle.com>
Tested-by: Herbert van den Bergh <herbert.van.den.bergh@oracle.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2012-02-03 16:16:41 -08:00