From: Ming Lei <ming.lei@redhat.com>
To: Bart Van Assche <Bart.VanAssche@wdc.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"jianchao.w.wang@oracle.com" <jianchao.w.wang@oracle.com>,
"axboe@kernel.dk" <axboe@kernel.dk>
Subject: Re: [RFC] blk-mq: clean up the hctx restart
Date: Fri, 3 Aug 2018 08:35:08 +0800 [thread overview]
Message-ID: <20180803003507.GE16047@ming.t460p> (raw)
In-Reply-To: <4868e0b82ac6e87aede7fc52da67d3a7913d680b.camel@wdc.com>
On Thu, Aug 02, 2018 at 05:24:15PM +0000, Bart Van Assche wrote:
> On Fri, 2018-08-03 at 01:17 +0800, Ming Lei wrote:
> > Not mentioning big CPU utilization is consumed unnecessarily for iterating
> > over all queues even though there is only one active queue, is this fair from
> > system view?
>
> I hope that someone will come up some day with a better solution than the
> list_for_each_entry_rcu_rr() loop. But as long as such a solution has not yet
> been found that loop should stay in order to preserve fair handling of large
> numbers of LUNs.
Again list_for_each_entry_rcu_rr() isn't fair for small number of active
queue in this case, because this way decreases IOPS a lot and consumes CPU
much just for checking all thousands of queues unnecessarily, even though 99%
of them are idle.
Thanks,
Ming
prev parent reply other threads:[~2018-08-03 0:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-31 4:02 [RFC] blk-mq: clean up the hctx restart Jianchao Wang
2018-07-31 4:58 ` Ming Lei
2018-07-31 5:19 ` jianchao.wang
2018-07-31 6:16 ` Ming Lei
2018-08-01 2:17 ` jianchao.wang
2018-08-01 8:58 ` Ming Lei
2018-08-01 13:37 ` jianchao.wang
2018-08-02 10:39 ` Ming Lei
2018-08-02 15:52 ` Bart Van Assche
2018-08-02 16:58 ` Ming Lei
2018-08-02 17:08 ` Bart Van Assche
2018-08-02 17:17 ` Ming Lei
2018-08-02 17:24 ` Bart Van Assche
2018-08-03 0:35 ` Ming Lei [this message]
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