linux-toradex.git/mm/compaction.c, branch v3.14.23

mm, compaction: ignore pageblock skip when manually invoking compaction

2014-10-09T19:21:28+00:00

commit 91ca9186484809c57303b33778d841cc28f696ed upstream.

The cached pageblock hint should be ignored when triggering compaction
through /proc/sys/vm/compact_memory so all eligible memory is isolated.
Manually invoking compaction is known to be expensive, there's no need
to skip pageblocks based on heuristics (mainly for debugging).

Signed-off-by: David Rientjes 
Acked-by: Mel Gorman 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm, compaction: determine isolation mode only once

2014-10-09T19:21:28+00:00

commit da1c67a76f7cf2b3404823d24f9f10fa91aa5dc5 upstream.

The conditions that control the isolation mode in
isolate_migratepages_range() do not change during the iteration, so
extract them out and only define the value once.

This actually does have an effect, gcc doesn't optimize it itself because
of cc->sync.

Signed-off-by: David Rientjes 
Cc: Mel Gorman 
Acked-by: Rik van Riel 
Acked-by: Vlastimil Babka 
Cc: Joonsoo Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm/compaction: clean-up code on success of ballon isolation

2014-10-09T19:21:28+00:00

commit b6c750163c0d138f5041d95fcdbd1094b6928057 upstream.

It is just for clean-up to reduce code size and improve readability.
There is no functional change.

Signed-off-by: Joonsoo Kim 
Acked-by: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm/compaction: check pageblock suitability once per pageblock

2014-10-09T19:21:28+00:00

commit c122b2087ab94192f2b937e47b563a9c4e688ece upstream.

isolation_suitable() and migrate_async_suitable() is used to be sure
that this pageblock range is fine to be migragted.  It isn't needed to
call it on every page.  Current code do well if not suitable, but, don't
do well when suitable.

1) It re-checks isolation_suitable() on each page of a pageblock that was
   already estabilished as suitable.
2) It re-checks migrate_async_suitable() on each page of a pageblock that
   was not entered through the next_pageblock: label, because
   last_pageblock_nr is not otherwise updated.

This patch fixes situation by 1) calling isolation_suitable() only once
per pageblock and 2) always updating last_pageblock_nr to the pageblock
that was just checked.

Additionally, move PageBuddy() check after pageblock unit check, since
pageblock check is the first thing we should do and makes things more
simple.

[vbabka@suse.cz: rephrase commit description]
Signed-off-by: Joonsoo Kim 
Acked-by: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm/compaction: change the timing to check to drop the spinlock

2014-10-09T19:21:28+00:00

commit be1aa03b973c7dcdc576f3503f7a60429825c35d upstream.

It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th
pfn page.  This may results in below situation while isolating
migratepage.

1. try isolate 0x0 ~ 0x200 pfn pages.
2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop
   the spinlock.
3. Then, to complete isolating, retry to aquire the lock.

I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking the
criteria about dropping the lock.  This has no harm 0x0 pfn, because, at
this time, locked variable would be false.

Signed-off-by: Joonsoo Kim 
Acked-by: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm/compaction: do not call suitable_migration_target() on every page

2014-10-09T19:21:28+00:00

commit 01ead5340bcf5f3a1cd2452c75516d0ef4d908d7 upstream.

suitable_migration_target() checks that pageblock is suitable for
migration target.  In isolate_freepages_block(), it is called on every
page and this is inefficient.  So make it called once per pageblock.

suitable_migration_target() also checks if page is highorder or not, but
it's criteria for highorder is pageblock order.  So calling it once
within pageblock range has no problem.

Signed-off-by: Joonsoo Kim 
Acked-by: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm/compaction: disallow high-order page for migration target

2014-10-09T19:21:28+00:00

commit 7d348b9ea64db0a315d777ce7d4b06697f946503 upstream.

Purpose of compaction is to get a high order page.  Currently, if we
find high-order page while searching migration target page, we break it
to order-0 pages and use them as migration target.  It is contrary to
purpose of compaction, so disallow high-order page to be used for
migration target.

Additionally, clean-up logic in suitable_migration_target() to simplify
the code.  There is no functional changes from this clean-up.

Signed-off-by: Joonsoo Kim 
Acked-by: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm, compaction: avoid isolating pinned pages

2014-10-09T19:21:28+00:00

commit 119d6d59dcc0980dcd581fdadb6b2033b512a473 upstream.

Page migration will fail for memory that is pinned in memory with, for
example, get_user_pages().  In this case, it is unnecessary to take
zone->lru_lock or isolating the page and passing it to page migration
which will ultimately fail.

This is a racy check, the page can still change from under us, but in
that case we'll just fail later when attempting to move the page.

This avoids very expensive memory compaction when faulting transparent
hugepages after pinning a lot of memory with a Mellanox driver.

On a 128GB machine and pinning ~120GB of memory, before this patch we
see the enormous disparity in the number of page migration failures
because of the pinning (from /proc/vmstat):

	compact_pages_moved 8450
	compact_pagemigrate_failed 15614415

0.05% of pages isolated are successfully migrated and explicitly
triggering memory compaction takes 102 seconds.  After the patch:

	compact_pages_moved 9197
	compact_pagemigrate_failed 7

99.9% of pages isolated are now successfully migrated in this
configuration and memory compaction takes less than one second.

Signed-off-by: David Rientjes 
Acked-by: Hugh Dickins 
Acked-by: Mel Gorman 
Cc: Joonsoo Kim 
Cc: Rik van Riel 
Cc: Greg Thelen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman

mm/compaction: make isolate_freepages start at pageblock boundary

2014-06-07T17:28:17+00:00

commit 49e068f0b73dd042c186ffa9b420a9943e90389a upstream.

The compaction freepage scanner implementation in isolate_freepages()
starts by taking the current cc->free_pfn value as the first pfn.  In a
for loop, it scans from this first pfn to the end of the pageblock, and
then subtracts pageblock_nr_pages from the first pfn to obtain the first
pfn for the next for loop iteration.

This means that when cc->free_pfn starts at offset X rather than being
aligned on pageblock boundary, the scanner will start at offset X in all
scanned pageblock, ignoring potentially many free pages.  Currently this
can happen when

 a) zone's end pfn is not pageblock aligned, or

 b) through zone->compact_cached_free_pfn with CONFIG_HOLES_IN_ZONE
    enabled and a hole spanning the beginning of a pageblock

This patch fixes the problem by aligning the initial pfn in
isolate_freepages() to pageblock boundary.  This also permits replacing
the end-of-pageblock alignment within the for loop with a simple
pageblock_nr_pages increment.

Signed-off-by: Vlastimil Babka 
Reported-by: Heesub Shin 
Acked-by: Minchan Kim 
Cc: Mel Gorman 
Acked-by: Joonsoo Kim 
Cc: Bartlomiej Zolnierkiewicz 
Cc: Michal Nazarewicz 
Cc: Naoya Horiguchi 
Cc: Christoph Lameter 
Acked-by: Rik van Riel 
Cc: Dongjun Shin 
Cc: Sunghwan Yun 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/compaction: break out of loop on !PageBuddy in isolate_freepages_block

2014-03-11T00:26:20+00:00

We received several reports of bad page state when freeing CMA pages
previously allocated with alloc_contig_range:

    BUG: Bad page state in process Binder_A  pfn:63202
    page:d21130b0 count:0 mapcount:1 mapping:  (null) index:0x7dfbf
    page flags: 0x40080068(uptodate|lru|active|swapbacked)

Based on the page state, it looks like the page was still in use.  The
page flags do not make sense for the use case though.  Further debugging
showed that despite alloc_contig_range returning success, at least one
page in the range still remained in the buddy allocator.

There is an issue with isolate_freepages_block.  In strict mode (which
CMA uses), if any pages in the range cannot be isolated,
isolate_freepages_block should return failure 0.  The current check
keeps track of the total number of isolated pages and compares against
the size of the range:

        if (strict && nr_strict_required > total_isolated)
                total_isolated = 0;

After taking the zone lock, if one of the pages in the range is not in
the buddy allocator, we continue through the loop and do not increment
total_isolated.  If in the last iteration of the loop we isolate more
than one page (e.g.  last page needed is a higher order page), the check
for total_isolated may pass and we fail to detect that a page was
skipped.  The fix is to bail out if the loop immediately if we are in
strict mode.  There's no benfit to continuing anyway since we need all
pages to be isolated.  Additionally, drop the error checking based on
nr_strict_required and just check the pfn ranges.  This matches with
what isolate_freepages_range does.

Signed-off-by: Laura Abbott 
Acked-by: Minchan Kim 
Cc: Mel Gorman 
Acked-by: Vlastimil Babka 
Cc: Joonsoo Kim 
Acked-by: Bartlomiej Zolnierkiewicz 
Acked-by: Michal Nazarewicz 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds