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>,
Laurence Oberman <loberman@redhat.com>,
linux-scsi@vger.kernel.org, Omar Sandoval <osandov@fb.com>,
John Garry <john.garry@huawei.com>
Subject: Re: [PATCH] SCSI: don't get target/host busy_count in scsi_mq_get_budget()
Date: Sat, 4 Nov 2017 08:19:58 -0600 [thread overview]
Message-ID: <adb7f6bd-bf0d-8176-808b-32a84ac4273a@kernel.dk> (raw)
In-Reply-To: <20171104015534.32684-1-ming.lei@redhat.com>
On 11/03/2017 07:55 PM, Ming Lei wrote:
> It is very expensive to atomic_inc/atomic_dec the host wide counter of
> host->busy_count, and it should have been avoided via blk-mq's mechanism
> of getting driver tag, which uses the more efficient way of sbitmap queue.
>
> Also we don't check atomic_read(&sdev->device_busy) in scsi_mq_get_budget()
> and don't run queue if the counter becomes zero, so IO hang may be caused
> if all requests are completed just before the current SCSI device
> is added to shost->starved_list.
This looks like an improvement. I have added it for 4.15.
Bart, does this fix your hang?
--
Jens Axboe
next prev parent reply other threads:[~2017-11-04 14:20 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-04 1:55 [PATCH] SCSI: don't get target/host busy_count in scsi_mq_get_budget() Ming Lei
2017-11-04 14:19 ` Jens Axboe [this message]
2017-11-06 19:45 ` Bart Van Assche
2017-11-07 2:11 ` Ming Lei
2017-11-07 16:20 ` Bart Van Assche
2017-11-07 16:29 ` Jens Axboe
2017-11-07 17:10 ` Jens Axboe
2017-11-07 17:36 ` Jens Axboe
2017-11-07 22:06 ` Jens Axboe
2017-11-07 22:34 ` Bart Van Assche
2017-11-07 22:39 ` Jens Axboe
2017-11-08 0:50 ` Ming Lei
2017-11-08 1:03 ` Ming Lei
2017-11-08 3:01 ` Jens Axboe
2017-11-08 3:12 ` Ming Lei
2017-11-08 3:17 ` Jens Axboe
2017-11-08 6:20 ` Ming Lei
2017-11-08 15:59 ` Ming Lei
2017-11-08 18:19 ` Jens Axboe
2017-11-07 17:34 ` Bart Van Assche
2017-11-08 0:53 ` Ming Lei
2017-11-08 2:06 ` Ming Lei
2017-11-08 0:39 ` Ming Lei
2017-11-08 2:55 ` Jens Axboe
2017-11-08 2:58 ` Ming Lei
2017-11-08 3:06 ` Jens Axboe
2017-11-08 16:41 ` Bart Van Assche
2017-11-08 17:57 ` Jens Axboe
2017-11-08 18:22 ` Laurence Oberman
2017-11-08 18:28 ` Jens Axboe
2017-11-09 4:02 ` Ming Lei
2017-11-09 2:05 ` Ming Lei
2017-11-07 10:15 ` Ming Lei
2017-11-07 16:17 ` Bart Van Assche
2017-11-08 3:12 ` Jens Axboe
2017-11-06 18:04 ` Bart Van Assche
2017-11-07 2:19 ` Ming Lei
2017-11-07 3:53 ` Martin K. Petersen
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