• Minchan Kim's avatar
    zram: set BDI_CAP_STABLE_WRITES once · e447a015
    Minchan Kim authored
    With fast swap storage, the platform wants 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 patchset reduces swap-in latency by skipping swapcache if the swap
    device is a synchronous device like a rw_page() based device.
    It enhances by 45% my swapin test (5G sequential swapin, no readahead)
    from 2.41sec to 1.64sec.
    This patch (of 4):
    Commit 19b7ccf8 ("block: get rid of blk_integrity_revalidate()")
    fixed a weird thing (i.e., reset BDI_CAP_STABLE_WRITES flag
    unconditionally whenever revalidat_disk is called) so zram doesn't need
    to reset the flag any more when revalidating the bdev.  Instead, set the
    flag just once when the zram device is created.
    It shouldn't change any behavior.
    Link: http://lkml.kernel.org/r/1505886205-9671-2-git-send-email-minchan@kernel.orgSigned-off-by: default avatarMinchan Kim <minchan@kernel.org>
    Reviewed-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
    Cc: Ilya Dryomov <idryomov@gmail.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Huang Ying <ying.huang@intel.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
zram_drv.c 40.5 KB