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    Subject[PATCH -next 0/3] md/raid10: reduce lock contention for io
    Date
    From: Yu Kuai <yukuai3@huawei.com>

    patch 1 is a small problem found by code review.
    patch 2 avoid holding resync_lock in fast path.
    patch 3 avoid holding lock in wake_up() in fast path.

    Test environment:

    Architecture: aarch64
    Cpu: Huawei KUNPENG 920, there are four numa nodes

    Raid10 initialize:
    mdadm --create /dev/md0 --level 10 --bitmap none --raid-devices 4 /dev/nvme0n1 /dev/nvme1n1 /dev/nvme2n1 /dev/nvme3n1

    Test cmd:
    fio -name=0 -ioengine=libaio -direct=1 -group_reporting=1 -randseed=2022 -rwmixread=70 -refill_buffers -filename=/dev/md0 -numjobs=16 -runtime=60s -bs=4k -iodepth=256 -rw=randread

    Test result:
    before this patchset: 2.9 GiB/s
    after this patchset: 6.6 Gib/s

    Please noted that in kunpeng-920, memory access latency is very bad
    accross nodes compare to local node, and in other architecture
    performance improvement might not be significant.

    Yu Kuai (3):
    md/raid10: fix improper BUG_ON() in raise_barrier()
    md/raid10: convert resync_lock to use seqlock
    md/raid10: prevent unnecessary calls to wake_up() in fast path

    drivers/md/raid10.c | 88 +++++++++++++++++++++++++++++----------------
    drivers/md/raid10.h | 2 +-
    2 files changed, 59 insertions(+), 31 deletions(-)

    --
    2.31.1

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