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When CONFIG_COMPACTION is enabled, compaction_deferred() tries to
recalculate the deferred limit again, which isn't necessary.
When CONFIG_COMPACTION is disabled, compaction_deferred() should return
"true" or "false" since it has "bool" for its return value.
Signed-off-by: Gavin Shan <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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This reverts commit 5ceb9ce6fe9462a298bb2cd5c9f1ca6cb80a0199.
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 <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Acked-by: KOSAKI Motohiro <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Cc: Bartlomiej Zolnierkiewicz <[email protected]>
Cc: Kyungmin Park <[email protected]>
Cc: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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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
[[email protected]: minor cleanups]
Cc: Mel Gorman <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[email protected]>
Signed-off-by: Kyungmin Park <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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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 <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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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.
[[email protected]: reduce scope of zones_need_compaction]
Signed-off-by: Rik van Riel <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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There's no compact_zone_order() user outside file scope, so make it static.
Signed-off-by: Kyungmin Park <[email protected]>
Acked-by: David Rientjes <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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This patch reverts 5a03b051 ("thp: use compaction in kswapd for GFP_ATOMIC
order > 0") due to reports stating that kswapd CPU usage was higher and
IRQs were being disabled more frequently. This was reported at
http://www.spinics.net/linux/fedora/alsa-user/msg09885.html.
Without this patch applied, CPU usage by kswapd hovers around the 20% mark
according to the tester (Arthur Marsh:
http://www.spinics.net/linux/fedora/alsa-user/msg09899.html). With this
patch applied, it's around 2%.
The problem is not related to THP which specifies __GFP_NO_KSWAPD but is
triggered by high-order allocations hitting the low watermark for their
order and waking kswapd on kernels with CONFIG_COMPACTION set. The most
common trigger for this is network cards configured for jumbo frames but
it's also possible it'll be triggered by fork-heavy workloads (order-1)
and some wireless cards which depend on order-1 allocations.
The symptoms for the user will be high CPU usage by kswapd in low-memory
situations which could be confused with another writeback problem. While
a patch like 5a03b051 may be reintroduced in the future, this patch plays
it safe for now and reverts it.
[[email protected]: Beefed up the changelog]
Signed-off-by: Andrea Arcangeli <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
Reported-by: Arthur Marsh <[email protected]>
Tested-by: Arthur Marsh <[email protected]>
Cc: <[email protected]> [2.6.38.1]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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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 <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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synchronous compaction in the faster path
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.
[[email protected]: build/merge fix]
Signed-off-by: Mel Gorman <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Rik van Riel <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: Andy Whitcroft <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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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()).
[[email protected]: fix build]
[[email protected]: use conventional task_struct naming]
Signed-off-by: Mel Gorman <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Rik van Riel <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: Andy Whitcroft <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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compaction fails
The fragmentation index may indicate that a failure is due to external
fragmentation but after a compaction run completes, it is still possible
for an allocation to fail. There are two obvious reasons as to why
o Page migration cannot move all pages so fragmentation remains
o A suitable page may exist but watermarks are not met
In the event of compaction followed by an allocation failure, this patch
defers further compaction in the zone (1 << compact_defer_shift) times.
If the next compaction attempt also fails, compact_defer_shift is
increased up to a maximum of 6. If compaction succeeds, the defer
counters are reset again.
The zone that is deferred is the first zone in the zonelist - i.e. the
preferred zone. To defer compaction in the other zones, the information
would need to be stored in the zonelist or implemented similar to the
zonelist_cache. This would impact the fast-paths and is not justified at
this time.
Signed-off-by: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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and when it should be reclaimed
The kernel applies some heuristics when deciding if memory should be
compacted or reclaimed to satisfy a high-order allocation. One of these
is based on the fragmentation. If the index is below 500, memory will not
be compacted. This choice is arbitrary and not based on data. To help
optimise the system and set a sensible default for this value, this patch
adds a sysctl extfrag_threshold. The kernel will only compact memory if
the fragmentation index is above the extfrag_threshold.
[[email protected]: Fix build errors when proc fs is not configured]
Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Ordinarily when a high-order allocation fails, direct reclaim is entered
to free pages to satisfy the allocation. With this patch, it is
determined if an allocation failed due to external fragmentation instead
of low memory and if so, the calling process will compact until a suitable
page is freed. Compaction by moving pages in memory is considerably
cheaper than paging out to disk and works where there are locked pages or
no swap. If compaction fails to free a page of a suitable size, then
reclaim will still occur.
Direct compaction returns as soon as possible. As each block is
compacted, it is checked if a suitable page has been freed and if so, it
returns.
[[email protected]: Fix build errors]
[[email protected]: fix count_vm_event preempt in memory compaction direct reclaim]
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Andrea Arcangeli <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Add a per-node sysfs file called compact. When the file is written to,
each zone in that node is compacted. The intention that this would be
used by something like a job scheduler in a batch system before a job
starts so that the job can allocate the maximum number of hugepages
without significant start-up cost.
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Reviewed-by: KOSAKI Motohiro <[email protected]>
Reviewed-by: Christoph Lameter <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Reviewed-by: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Add a proc file /proc/sys/vm/compact_memory. When an arbitrary value is
written to the file, all zones are compacted. The expected user of such a
trigger is a job scheduler that prepares the system before the target
application runs.
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Reviewed-by: KAMEZAWA Hiroyuki <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Reviewed-by: KOSAKI Motohiro <[email protected]>
Reviewed-by: Christoph Lameter <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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This patch is the core of a mechanism which compacts memory in a zone by
relocating movable pages towards the end of the zone.
A single compaction run involves a migration scanner and a free scanner.
Both scanners operate on pageblock-sized areas in the zone. The migration
scanner starts at the bottom of the zone and searches for all movable
pages within each area, isolating them onto a private list called
migratelist. The free scanner starts at the top of the zone and searches
for suitable areas and consumes the free pages within making them
available for the migration scanner. The pages isolated for migration are
then migrated to the newly isolated free pages.
[[email protected]: Fix unsafe optimisation]
[[email protected]: do not schedule work on other CPUs for compaction]
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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