linux-toradex.git/mm/compaction.c, branch v2.6.38-rc8

mm: compaction: prevent division-by-zero during user-requested compaction

2011-01-21T01:02:05+00:00

Up until 3e7d344 ("mm: vmscan: reclaim order-0 and use compaction instead
of lumpy reclaim"), compaction skipped calculating the fragmentation index
of a zone when compaction was explicitely requested through the procfs
knob.

However, when compaction_suitable was introduced, it did not come with an
extra check for order == -1, set on explicit compaction requests, and
passed this order on to the fragmentation index calculation, where it
overshifts the number of requested pages, leading to a division by zero.

This patch makes sure that order == -1 is recognized as the flag it is
rather than passing it along as valid order parameter.

[akpm@linux-foundation.org: add comment, per Mel]
Signed-off-by: Johannes Weiner 
Reviewed-by: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

thp: use compaction for all allocation orders

2011-01-14T01:32:46+00:00

It makes no sense not to enable compaction for small order pages as we
don't want to end up with bad order 2 allocations and good and graceful
order 9 allocations.

Signed-off-by: Andrea Arcangeli 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

thp: use compaction in kswapd for GFP_ATOMIC order > 0

2011-01-14T01:32:46+00:00

This takes advantage of memory compaction to properly generate pages of
order > 0 if regular page reclaim fails and priority level becomes more
severe and we don't reach the proper watermarks.

Signed-off-by: Andrea Arcangeli 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

thp: transhuge isolate_migratepages()

2011-01-14T01:32:45+00:00

It's not worth migrating transparent hugepages during compaction.  Those
hugepages don't create fragmentation.

Signed-off-by: Andrea Arcangeli 
Acked-by: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: compaction: perform a faster migration scan when migrating asynchronously

2011-01-14T01:32:34+00:00

try_to_compact_pages() is initially called to only migrate pages
asychronously and kswapd always compacts asynchronously.  Both are being
optimistic so it is important to complete the work as quickly as possible
to minimise stalls.

This patch alters the scanner when asynchronous to only consider
MIGRATE_MOVABLE pageblocks as migration candidates.  This reduces stalls
when allocating huge pages while not impairing allocation success rates as
a full scan will be performed if necessary after direct reclaim.

Signed-off-by: Mel Gorman 
Cc: Andrea Arcangeli 
Cc: KOSAKI Motohiro 
Cc: Rik van Riel 
Acked-by: Johannes Weiner 
Cc: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: migration: cleanup migrate_pages API by matching types for offlining and sync

2011-01-14T01:32:34+00:00

With the introduction of the boolean sync parameter, the API looks a
little inconsistent as offlining is still an int.  Convert offlining to a
bool for the sake of being tidy.

Signed-off-by: Mel Gorman 
Cc: Andrea Arcangeli 
Cc: KOSAKI Motohiro 
Cc: Rik van Riel 
Acked-by: Johannes Weiner 
Cc: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: migration: allow migration to operate asynchronously and avoid synchronous compaction in the faster path

2011-01-14T01:32:34+00:00

Migration synchronously waits for writeback if the initial passes fails.
Callers of memory compaction do not necessarily want this behaviour if the
caller is latency sensitive or expects that synchronous migration is not
going to have a significantly better success rate.

This patch adds a sync parameter to migrate_pages() allowing the caller to
indicate if wait_on_page_writeback() is allowed within migration or not.
For reclaim/compaction, try_to_compact_pages() is first called
asynchronously, direct reclaim runs and then try_to_compact_pages() is
called synchronously as there is a greater expectation that it'll succeed.

[akpm@linux-foundation.org: build/merge fix]
Signed-off-by: Mel Gorman 
Cc: Andrea Arcangeli 
Cc: KOSAKI Motohiro 
Cc: Rik van Riel 
Acked-by: Johannes Weiner 
Cc: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: vmscan: reclaim order-0 and use compaction instead of lumpy reclaim

2011-01-14T01:32:33+00:00

Lumpy reclaim is disruptive.  It reclaims a large number of pages and
ignores the age of the pages it reclaims.  This can incur significant
stalls and potentially increase the number of major faults.

Compaction has reached the point where it is considered reasonably stable
(meaning it has passed a lot of testing) and is a potential candidate for
displacing lumpy reclaim.  This patch introduces an alternative to lumpy
reclaim whe compaction is available called reclaim/compaction.  The basic
operation is very simple - instead of selecting a contiguous range of
pages to reclaim, a number of order-0 pages are reclaimed and then
compaction is later by either kswapd (compact_zone_order()) or direct
compaction (__alloc_pages_direct_compact()).

[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: use conventional task_struct naming]
Signed-off-by: Mel Gorman 
Cc: Andrea Arcangeli 
Cc: KOSAKI Motohiro 
Cc: Rik van Riel 
Acked-by: Johannes Weiner 
Cc: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: compaction: add trace events for memory compaction activity

2011-01-14T01:32:33+00:00

In preparation for a patches promoting the use of memory compaction over
lumpy reclaim, this patch adds trace points for memory compaction
activity.  Using them, we can monitor the scanning activity of the
migration and free page scanners as well as the number and success rates
of pages passed to page migration.

Signed-off-by: Mel Gorman 
Cc: Andrea Arcangeli 
Cc: KOSAKI Motohiro 
Cc: Rik van Riel 
Cc: Johannes Weiner 
Cc: Andy Whitcroft 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/compaction.c: avoid double mem_cgroup_del_lru()

2010-12-23T03:43:33+00:00

del_page_from_lru_list() already called mem_cgroup_del_lru().  So we must
not call it again.  It adds unnecessary overhead.

It was not a runtime bug because the TestClearPageCgroupAcctLRU() early in
mem_cgroup_del_lru_list() will prevent any double-deletion, etc.

Signed-off-by: Minchan Kim 
Acked-by: Balbir Singh 
Acked-by: KAMEZAWA Hiroyuki 
Acked-by: Mel Gorman 
Reviewed-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds