From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "axboe@kernel.dk" <axboe@kernel.dk>,
"ming.lei@redhat.com" <ming.lei@redhat.com>
Cc: "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"osandov@fb.com" <osandov@fb.com>,
"john.garry@huawei.com" <john.garry@huawei.com>,
"loberman@redhat.com" <loberman@redhat.com>
Subject: Re: [PATCH] SCSI: don't get target/host busy_count in scsi_mq_get_budget()
Date: Tue, 7 Nov 2017 22:34:35 +0000 [thread overview]
Message-ID: <1510094074.2656.39.camel@wdc.com> (raw)
In-Reply-To: <a6a505f5-d374-2878-6c55-116255795346@kernel.dk>
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WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "axboe@kernel.dk" <axboe@kernel.dk>,
"ming.lei@redhat.com" <ming.lei@redhat.com>
Cc: "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"osandov@fb.com" <osandov@fb.com>,
"john.garry@huawei.com" <john.garry@huawei.com>,
"loberman@redhat.com" <loberman@redhat.com>
Subject: Re: [PATCH] SCSI: don't get target/host busy_count in scsi_mq_get_budget()
Date: Tue, 7 Nov 2017 22:34:35 +0000 [thread overview]
Message-ID: <1510094074.2656.39.camel@wdc.com> (raw)
In-Reply-To: <a6a505f5-d374-2878-6c55-116255795346@kernel.dk>
On Tue, 2017-11-07 at 15:06 -0700, Jens Axboe wrote:
> Just to keep everyone in the loop, this bug is not new to
> for-4.15/block, nor is it new to the current 4.41-rc or 4.13. So it's
> probably different to what Bart is hitting, but it's a bug none the
> less...
Hello Jens,
There are several reasons why I think that patch "blk-mq: don't handle
TAG_SHARED in restart" really should be reverted:
* That patch is based on the assumption that only the SCSI driver uses shared
tags. That assumption is not correct. null_blk and nvme also use shared tags.
* As my tests have shown, the algorithm for restarting queues based on the
SCSI starved list is flawed. So using that mechanism instead of the blk-mq
shared queue restarting algorithm is wrong.
* We are close to the merge window. It is too late for trying to fix the
"blk-mq: don't handle TAG_SHARED in restart" patch.
My proposal is to make sure that what will be sent to Linus during the v4.15
merge window works reliably. That means using the v4.13/v4.14 algorithm for
queue restarting which is an algorithm that is trusted by the community. If
Roman Penyaev's patch could get applied that would be even better.
Bart.
next prev parent reply other threads:[~2017-11-07 22:34 UTC|newest]
Thread overview: 47+ 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
2017-11-06 19:45 ` Bart Van Assche
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 16:20 ` 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 [this message]
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 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
2017-11-07 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 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
2017-11-07 16:17 ` Bart Van Assche
2017-11-08 3:12 ` Jens Axboe
2017-11-06 18:04 ` Bart Van Assche
2017-11-06 18:04 ` Bart Van Assche
2017-11-07 2:19 ` Ming Lei
2017-11-07 3:53 ` Martin K. Petersen
2017-11-07 3:53 ` Martin K. Petersen
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