Messages in this thread | | | Date | Wed, 31 Aug 2022 13:59:38 +0200 | Subject | Re: [PATCH -next 0/3] md/raid10: reduce lock contention for io | From | Paul Menzel <> |
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Dear Yu,
Am 30.08.22 um 03:09 schrieb Yu Kuai:
> 在 2022/08/29 21:58, Paul Menzel 写道:
>> Am 29.08.22 um 15:14 schrieb Yu Kuai: >>> 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 >> >> Could you please give more details about the test setup, like the >> drives used? > > test setup is described above, four nvme disks is used.
I was wondering about the model to be able to reproduce it.
>> Did you use some tools like ftrace to figure out the bottleneck? > > Yes, I'm sure the bottleneck is spin_lock(), specifically threads from > multiple nodes try to grab the same lock. By the way, if I bind the > threads to the same node, performance can also improve to 6.6 Gib/s > without this patchset.
Interesting. Maybe you could add all that to the commit message of the second patch.
Kind regards,
Paul
>>> 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(-)
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