From: Jens Axboe <axboe@kernel.dk>
To: Ming Lei <ming.lei@redhat.com>,
linux-block@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>
Cc: Bart Van Assche <bart.vanassche@sandisk.com>,
Sagi Grimberg <sagi@grimberg.me>
Subject: Re: [PATCH 4/6] blk-mq: use EWMA to estimate congestion threshold
Date: Tue, 11 Jul 2017 12:25:16 -0600 [thread overview]
Message-ID: <db7526a0-d534-8bc2-93de-546f4dabccfb@kernel.dk> (raw)
In-Reply-To: <20170711182103.11461-5-ming.lei@redhat.com>
On 07/11/2017 12:21 PM, Ming Lei wrote:
> When .queue_rq() returns BLK_STS_RESOURCE(BUSY), we can
> consider that there is congestion in either low level
> driver or hardware.
>
> This patch uses EWMA to estimate this congestion threshold,
> then this threshold can be used to detect/avoid congestion.
This whole patch set lacks some sort of reasoning why this
makes sense. I'm assuming you want to reduce unnecessary
restarts of the queue? I would much rather ensure that we only
start when we absolutely have to to begin with, I'm pretty sure
we have a number of cases where that is not so.
What happens with fluid congestion boundaries, with shared tags?
--
Jens Axboe
next prev parent reply other threads:[~2017-07-11 18:25 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-11 18:20 [PATCH 0/6] blk-mq: introduce congestion control Ming Lei
2017-07-11 18:20 ` [PATCH 1/6] xen-blkfront: avoid to use start/stop queue Ming Lei
2017-07-11 18:41 ` Konrad Rzeszutek Wilk
2017-07-12 2:52 ` Ming Lei
2017-07-11 18:41 ` Bart Van Assche
2017-07-12 2:59 ` Ming Lei
2017-07-12 3:05 ` Ming Lei
2017-07-11 21:24 ` Roger Pau Monné
2017-07-12 3:12 ` Ming Lei
2017-07-11 18:20 ` [PATCH 2/6] SCSI: use blk_mq_run_hw_queues() in scsi_kick_queue() Ming Lei
2017-07-11 19:57 ` Bart Van Assche
2017-07-12 3:15 ` Ming Lei
2017-07-12 15:12 ` Bart Van Assche
2017-07-13 10:23 ` Ming Lei
2017-07-13 17:44 ` Bart Van Assche
2017-07-11 18:21 ` [PATCH 3/6] blk-mq: send the request to dispatch list if direct issue returns busy Ming Lei
2017-07-11 20:18 ` Bart Van Assche
2017-07-12 3:45 ` Ming Lei
2017-07-11 18:21 ` [PATCH 4/6] blk-mq: use EWMA to estimate congestion threshold Ming Lei
2017-07-11 18:25 ` Jens Axboe [this message]
2017-07-12 2:30 ` Ming Lei
2017-07-12 15:39 ` Bart Van Assche
2017-07-13 10:43 ` Ming Lei
2017-07-13 14:56 ` Bart Van Assche
2017-07-13 15:32 ` Ming Lei
2017-07-13 17:35 ` Bart Van Assche
2017-07-11 18:39 ` Jens Axboe
2017-07-12 3:20 ` Ming Lei
2017-07-11 21:02 ` Bart Van Assche
2017-07-12 3:43 ` Ming Lei
2017-07-11 18:21 ` [PATCH 5/6] blk-mq: introduce basic congestion control Ming Lei
2017-07-11 18:21 ` [PATCH 6/6] blk-mq: unexport APIs for start/stop queues Ming Lei
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