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由 Minchan Kim 提交于
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: NMinchan Kim <minchan@kernel.org> Reported-by: NCai Liu <cai.liu@samsung.com> Suggested-by: NWeijie Yang <weijie.yang.kh@gmail.com> Cc: Seth Jennings <sjennings@variantweb.net> Reviewed-by: NBob Liu <bob.liu@oracle.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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