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mm, swap: skip swapcache for swapin of synchronous device
authorMinchan Kim <minchan@kernel.org>
Thu, 16 Nov 2017 01:33:07 +0000 (17:33 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 16 Nov 2017 02:21:02 +0000 (18:21 -0800)
commit0bcac06f27d7528591c27ac2b093ccd71c5d0168
treeb8261d05b232e57a58a7fe90306cad5d545de900
parent539a6fea7fdcade532bd3e77be2862a683f8f0c9
mm, swap: skip swapcache for swapin of synchronous device

With fast swap storage, the platforms want to use swap more aggressively
and swap-in is crucial to application latency.

The rw_page() based synchronous devices like zram, pmem and btt are such
fast storage.  When I profile swapin performance with zram lz4
decompress test, S/W overhead is more than 70%.  Maybe, it would be
bigger in nvdimm.

This patch aims to reduce swap-in latency by skipping swapcache if the
swap device is synchronous device like rw_page based device.  It
enhances 45% my swapin test(5G sequential swapin, no readahead, from
2.41sec to 1.64sec).

Link: http://lkml.kernel.org/r/1505886205-9671-5-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/swap.h
mm/memory.c
mm/page_io.c
mm/swapfile.c