Mel Gorman 283aba9f9e mm: vmscan: block kswapd if it is encountering pages under writeback ... Historically, kswapd used to congestion_wait() at higher priorities if it was not making forward progress. This made no sense as the failure to make progress could be completely independent of IO. It was later replaced by wait_iff_congested() and removed entirely by commit 258401a6 (mm: don't wait on congested zones in balance_pgdat()) as it was duplicating logic in shrink_inactive_list(). This is problematic. If kswapd encounters many pages under writeback and it continues to scan until it reaches the high watermark then it will quickly skip over the pages under writeback and reclaim clean young pages or push applications out to swap. The use of wait_iff_congested() is not suited to kswapd as it will only stall if the underlying BDI is really congested or a direct reclaimer was unable to write to the underlying BDI. kswapd bypasses the BDI congestion as it sets PF_SWAPWRITE but even if this was taken into account then it would cause direct reclaimers to stall on writeback which is not desirable. This patch sets a ZONE_WRITEBACK flag if direct reclaim or kswapd is encountering too many pages under writeback. If this flag is set and kswapd encounters a PageReclaim page under writeback then it'll assume that the LRU lists are being recycled too quickly before IO can complete and block waiting for some IO to complete. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Michal Hocko <mhocko@suse.cz> Acked-by: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu> Tested-by: Zlatko Calusic <zcalusic@bitsync.net> Cc: dormando <dormando@rydia.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2013-07-03 16:07:28 -07:00
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acpi	ACPI / dock / PCI: Synchronous handling of dock events for PCI devices	2013-06-24 11:22:53 +02:00
asm-generic	mm: soft-dirty bits for user memory changes tracking	2013-07-03 16:07:26 -07:00
clocksource
crypto
drm
dt-bindings	ARM SoC driver specific changes	2013-07-02 14:33:21 -07:00
keys
linux	mm: vmscan: block kswapd if it is encountering pages under writeback	2013-07-03 16:07:28 -07:00
math-emu
media	Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media	2013-06-18 06:25:08 -10:00
memory
misc
net	ip_tunnel: remove __net_init/exit from exported functions	2013-06-13 03:00:59 -07:00
pcmcia
ras
rdma
rxrpc
scsi
sound
target
trace	Merge branch 'x86-tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2013-07-02 16:31:49 -07:00
uapi	Main features:	2013-07-03 10:31:38 -07:00
video
xen	Main features:	2013-07-03 10:31:38 -07:00
Kbuild