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authorMinchan Kim <minchan@kernel.org>2014-04-07 15:38:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-07 16:36:03 -0700
commit60105e1248f571aa3b895cd63bef072ed9d90c77 (patch)
tree9e0d526a18bfcfeed78905f2c6ca9b52792c2803 /include
parent6335b19344cc263724ae49a76ed930b21a659055 (diff)
downloadlinux-60105e1248f571aa3b895cd63bef072ed9d90c77.tar.bz2
mm/zswap: support multiple swap devices
Cai Liu reporeted that now zbud pool pages counting has a problem when multiple swap is used because it just counts only one swap intead of all of swap so zswap cannot control writeback properly. The result is unnecessary writeback or no writeback when we should really writeback. IOW, it made zswap crazy. Another problem in zswap is: For example, let's assume we use two swap A and B with different priority and A already has charged 19% long time ago and let's assume that A swap is full now so VM start to use B so that B has charged 1% recently. It menas zswap charged (19% + 1%) is full by default. Then, if VM want to swap out more pages into B, zbud_reclaim_page would be evict one of pages in B's pool and it would be repeated continuously. It's totally LRU reverse problem and swap thrashing in B would happen. This patch makes zswap consider mutliple swap by creating *a* zbud pool which will be shared by multiple swap so all of zswap pages in multiple swap keep order by LRU so it can prevent above two problems. Signed-off-by: Minchan Kim <minchan@kernel.org> Reported-by: Cai Liu <cai.liu@samsung.com> Suggested-by: Weijie Yang <weijie.yang.kh@gmail.com> Cc: Seth Jennings <sjennings@variantweb.net> Reviewed-by: Bob Liu <bob.liu@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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