From: Jens Axboe <axboe@kernel.dk>
To: Lin Feng <linf@wangsu.com>
Cc: linux-block@vger.kernel.org, ming.lei@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] blk-mq: bypass IO scheduler's limit_depth for passthrough request
Date: Fri, 16 Apr 2021 06:09:18 -0600 [thread overview]
Message-ID: <c8c572f3-ac49-5a9b-0ca0-6ec150bdb27c@kernel.dk> (raw)
In-Reply-To: <20210415033920.213963-1-linf@wangsu.com>
On 4/14/21 9:39 PM, Lin Feng wrote:
> Commit 01e99aeca39796003 ("blk-mq: insert passthrough request into
> hctx->dispatch directly") gives high priority to passthrough requests and
> bypass underlying IO scheduler. But as we allocate tag for such request it
> still runs io-scheduler's callback limit_depth, while we really want is to
> give full sbitmap-depth capabity to such request for acquiring available
> tag.
> blktrace shows PC requests(dmraid -s -c -i) hit bfq's limit_depth:
> 8,0 2 0 0.000000000 39952 1,0 m N bfq [bfq_limit_depth] wr_busy 0 sync 0 depth 8
> 8,0 2 1 0.000008134 39952 D R 4 [dmraid]
> 8,0 2 2 0.000021538 24 C R [0]
> 8,0 2 0 0.000035442 39952 1,0 m N bfq [bfq_limit_depth] wr_busy 0 sync 0 depth 8
> 8,0 2 3 0.000038813 39952 D R 24 [dmraid]
> 8,0 2 4 0.000044356 24 C R [0]
>
> This patch introduce a new wrapper to make code not that ugly.
Applied, thanks.
--
Jens Axboe
prev parent reply other threads:[~2021-04-16 12:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-15 3:39 [PATCH 1/2] blk-mq: bypass IO scheduler's limit_depth for passthrough request Lin Feng
2021-04-16 2:10 ` Ming Lei
2021-04-16 12:09 ` Jens Axboe [this message]
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