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authorJohannes Weiner <hannes@cmpxchg.org>2014-01-29 14:05:41 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-02-13 13:48:00 -0800
commit48526149964e69fc54a06c409e13d36990386464 (patch)
tree844e34d12c42f34711531573af92243fbf273ef8 /drivers
parent03381bd28963f97a976d4742468359f12474ea39 (diff)
downloadlinaro-lsk-48526149964e69fc54a06c409e13d36990386464.tar.gz
mm/page-writeback.c: do not count anon pages as dirtyable memory
commit a1c3bfb2f67ef766de03f1f56bdfff9c8595ab14 upstream. The VM is currently heavily tuned to avoid swapping. Whether that is good or bad is a separate discussion, but as long as the VM won't swap to make room for dirty cache, we can not consider anonymous pages when calculating the amount of dirtyable memory, the baseline to which dirty_background_ratio and dirty_ratio are applied. A simple workload that occupies a significant size (40+%, depending on memory layout, storage speeds etc.) of memory with anon/tmpfs pages and uses the remainder for a streaming writer demonstrates this problem. In that case, the actual cache pages are a small fraction of what is considered dirtyable overall, which results in an relatively large portion of the cache pages to be dirtied. As kswapd starts rotating these, random tasks enter direct reclaim and stall on IO. Only consider free pages and file pages dirtyable. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reported-by: Tejun Heo <tj@kernel.org> Tested-by: Tejun Heo <tj@kernel.org> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Wu Fengguang <fengguang.wu@intel.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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