From: John Garry <john.garry@huawei.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
<linux-block@vger.kernel.org>, Yanhui Ma <yama@redhat.com>,
Bart Van Assche <bvanassche@acm.org>,
<kashyap.desai@broadcom.com>,
chenxiang <chenxiang66@hisilicon.com>
Subject: Re: [PATCH] blk-mq: plug request for shared sbitmap
Date: Wed, 19 May 2021 09:41:01 +0100 [thread overview]
Message-ID: <aa667e0d-0b42-08c2-35e1-387e2e92dc43@huawei.com> (raw)
In-Reply-To: <YKRaGT5PjCvH+12p@T590>
On 19/05/2021 01:21, Ming Lei wrote:
>> The 'after' results are similar to without shared sbitmap, i.e using
>> reply-map:
>>
>> reply-map:
>> 450K (read), 430K IOPs (randread)
> OK, that is expected result. After shared sbitmap, IO merge gets improved
> when batching submission is bypassed, meantime IOPS of random IO drops
> because cpu utilization is increased.
>
> So that isn't a regression, let's live with this awkward situation,:-(
Well at least we have ~ parity with non-shared sbitmap now. And also
know higher performance is possible for "read" (vs "randread") scenario,
FWIW.
BTW, recently we have seen 2x optimisation/improvement for shared
sbitmap which were under/related to nr_hw_queues == 1 check - this patch
and the changing of the default IO sched.
I am wondering how you detected/analyzed this issue, and whether we need
to audit other nr_hw_queues == 1 checks? I did a quick scan, and the
only possible thing I see is the other q->nr_hw_queues > 1 check for
direct issue in blk_mq_subit_bio() - I suspect you know more about that
topic.
Thanks,
John
next prev parent reply other threads:[~2021-05-19 8:42 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-14 2:20 [PATCH] blk-mq: plug request for shared sbitmap Ming Lei
2021-05-14 14:59 ` Jens Axboe
2021-05-18 9:44 ` John Garry
2021-05-18 11:16 ` Ming Lei
2021-05-18 11:42 ` John Garry
2021-05-18 12:00 ` Ming Lei
2021-05-18 12:51 ` John Garry
2021-05-18 16:01 ` John Garry
2021-05-19 0:21 ` Ming Lei
2021-05-19 8:41 ` John Garry [this message]
2021-05-20 1:23 ` Ming Lei
2021-05-20 8:21 ` John Garry
2021-05-18 11:54 ` Hannes Reinecke
2021-05-18 12:37 ` John Garry
2021-05-18 13:22 ` Hannes Reinecke
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