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From: Ming Lei <ming.lei@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@vger.kernel.org,
	cgroups@vger.kernel.org, newella@fb.com, josef@toxicpanda.com
Subject: Re: [PATCH 2/5] block: add request->io_data_len
Date: Thu, 9 Apr 2020 09:44:06 +0800	[thread overview]
Message-ID: <20200409014406.GA370295@localhost.localdomain> (raw)
In-Reply-To: <20200408201450.3959560-3-tj@kernel.org>

Hi Tejun,

On Wed, Apr 08, 2020 at 04:14:47PM -0400, Tejun Heo wrote:
> Currently, at the time of completeion, there's no way of knowing how big a
> request was. blk-iocost will need this information to account for IO size when
> calculating expected latencies.
> 
> This patch adds rq->io_data_len which remembers blk_rq_bytes() at the time the
> request gets issued. The field is enabled iff CONFIG_BLK_IO_DATA_LEN is set and
> doesn't increase the size of the struct even when enabled.

Almost all __blk_mq_end_request() follow blk_update_request(), so the
completed bytes can be passed to __blk_mq_end_request(), then we can
avoid to introduce this field.

Also there is just 20 callers of __blk_mq_end_request(), looks this kind
of change shouldn't be too big.


Thanks, 
Ming


  reply	other threads:[~2020-04-09  1:44 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-08 20:14 [PATCHSET block/for-5.8] iocost: improve use_delay and latency target handling Tejun Heo
2020-04-08 20:14 ` [PATCH 1/5] blk-iocost: switch to fixed non-auto-decaying use_delay Tejun Heo
2020-04-08 20:14 ` [PATCH 2/5] block: add request->io_data_len Tejun Heo
2020-04-09  1:44   ` Ming Lei [this message]
2020-04-09  2:11     ` Tejun Heo
2020-04-09  2:38       ` Ming Lei
2020-04-09  5:08         ` Pavel Begunkov
2020-04-13 14:02           ` Tejun Heo
2020-04-13 13:56         ` Tejun Heo
2020-04-09  3:44   ` Bart Van Assche
2020-04-13 13:52     ` Tejun Heo
2020-04-08 20:14 ` [PATCH 3/5] blk-iocost: account for IO size when testing latencies Tejun Heo
2020-04-08 20:14 ` [PATCH 4/5] iocost_monitor: exit successfully if interval is zero Tejun Heo
2020-04-08 20:14 ` [PATCH 5/5] iocost_monitor: drop string wrap around numbers when outputting json Tejun Heo

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