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Andrea Arcangeli d527caf22e mm: compaction: prevent kswapd compacting memory to reduce CPU usage 
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.

[mel@csn.ul.ie: Beefed up the changelog]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reported-by: Arthur Marsh <arthur.marsh@internode.on.net>
Tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Cc: <stable@kernel.org>		[2.6.38.1]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
..
acpi PM: Remove CONFIG_PM_OPS 2011-03-15 00:43:15 +01:00
asm-generic include/asm-generic/unistd.h: fix syncfs syscall number 2011-03-22 17:43:58 -07:00
crypto crypto: padlock - Move padlock.h into include/crypto 2011-01-07 14:52:00 +11:00
drm Merge remote branch 'intel/drm-intel-next' of ../drm-next into drm-core-next 2011-03-14 14:15:13 +10:00
keys RxRPC: Fix v1 keys 2011-03-02 22:18:53 -08:00
linux mm: compaction: prevent kswapd compacting memory to reduce CPU usage 2011-03-22 17:44:00 -07:00
math-emu
media [media] v4l: Include linux/videodev2.h in media/v4l2-ctrls.h 2011-01-19 11:52:09 -02:00
mtd
net IPVS: Use global mutex in ip_vs_app.c 2011-03-21 20:39:24 -07:00
pcmcia pcmcia: re-enable Zoomed Video support 2011-02-20 12:47:34 +01:00
rdma RDMA: Update workqueue usage 2011-01-16 21:16:31 -08:00
rxrpc
scsi Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2011-03-17 17:54:40 -07:00
sound Merge branch 'topic/misc' into for-linus 2011-03-18 07:39:08 +01:00
target [SCSI] target: Fix t_transport_aborted handling in LUN_RESET + active I/O shutdown 2011-02-28 11:23:32 -06:00
trace Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6 2011-03-18 10:46:37 -07:00
video fbdev: sh_mobile_lcdc: Add YUV framebuffer support 2011-03-16 17:27:10 +09:00
xen Merge branch 'stable/xen.pm.bug-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2011-03-17 18:37:42 -07:00
Kbuild