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From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "ming.lei@redhat.com" <ming.lei@redhat.com>,
	"jianchao.w.wang@oracle.com" <jianchao.w.wang@oracle.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"axboe@kernel.dk" <axboe@kernel.dk>
Subject: Re: [RFC] blk-mq: clean up the hctx restart
Date: Thu, 2 Aug 2018 15:52:00 +0000	[thread overview]
Message-ID: <9feaa41702ef6fcc00ce1b8aa19bbe179edf4e3f.camel@wdc.com> (raw)
In-Reply-To: <20180801085841.GA27962@ming.t460p>

On Wed, 2018-08-01 at 16:58 +0800, Ming Lei wrote:
> On Wed, Aug 01, 2018 at 10:17:30AM +0800, jianchao.wang wrote:
> > However, due to the limits in hctx_may_queue, q_b still cannot get the
> > tags. The RR restart also will not wake up q_a.
> > This is unfair for q_a.
> > 
> > When we remove RR restart fashion, at least, the q_a will be waked up by
> > the hctx restart.
> > Is this the improvement of fairness you said in driver tag allocation ?
> 
> I mean the fairness is totally covered by the general tag allocation
> algorithm now, which is sort of FIFO style because of waitqueue, but RR
> restart wakes up queue in the order of request queue.

From sbitmap.h:

#define SBQ_WAIT_QUEUES 8

What do you think is the effect of your patch if more than eight LUNs are
active and the SCSI queue is full?

Thanks,

Bart.


  parent reply	other threads:[~2018-08-02 15:52 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-31  4:02 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 [this message]
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

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