From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>, Jeff Moyer <jmoyer@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
Markus Trippelsdorf <markus@trippelsdorf.de>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
linux-kernel@vger.kernel.org,
Chris Mason <chris.mason@oracle.com>
Subject: Re: [PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE
Date: Wed, 30 Mar 2011 09:59:09 +0200 [thread overview]
Message-ID: <4D92E2CD.6000909@kernel.dk> (raw)
In-Reply-To: <20110330075752.GC17523@htj.dyndns.org>
On 2011-03-30 09:57, Tejun Heo wrote:
> On Wed, Mar 30, 2011 at 09:41:23AM +0200, Tejun Heo wrote:
>> IIRC, at least in the requeue path, some drivers depend on front
>> queueing for forward progress guarantee. Forward progress for
>> prepping is guaranteed by mempool (or something like that) and when
>> the request is retried, it should stay at the front of the queue;
>> otherwise, prepping can stall with prepped requests stuck behind
>> unprepped ones.
>
> After writing the above, I think the current flush implementation
> actually is violating the above. I think the problem is over-use of
> front insertion. Flush can just append to the dispatch queue. Front
> insertion should only be used by requeueing, really.
Pure front insert should be used for requeue and internal commands (like
spin up this drive, or get error information). Flush should append to
the dispatch list.
--
Jens Axboe
next prev parent reply other threads:[~2011-03-30 7:59 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-25 15:15 [OOPS] elevator private data for REQ_FLUSH Sergey Senozhatsky
2011-03-25 15:22 ` Markus Trippelsdorf
2011-03-25 15:40 ` Mike Snitzer
2011-03-25 15:50 ` Jens Axboe
2011-03-25 18:54 ` Mike Snitzer
2011-03-25 19:50 ` Jens Axboe
2011-03-26 4:21 ` Mike Snitzer
2011-03-28 8:23 ` Tejun Heo
2011-03-28 22:15 ` [PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE (was: Re: elevator private data for REQ_FLUSH) Mike Snitzer
2011-03-29 11:56 ` [PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE Jens Axboe
2011-03-29 14:18 ` Mike Snitzer
2011-03-29 18:25 ` [PATCH] " Christoph Hellwig
2011-03-30 7:42 ` Tejun Heo
2011-03-30 7:53 ` Jens Axboe
2011-03-29 14:13 ` [PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE (was: Re: elevator private data for REQ_FLUSH) Jeff Moyer
2011-03-29 17:54 ` Vivek Goyal
2011-03-30 7:41 ` Tejun Heo
2011-03-30 7:57 ` Tejun Heo
2011-03-30 7:59 ` Jens Axboe [this message]
2011-03-30 8:02 ` [PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE Tejun Heo
2011-03-30 10:16 ` Jens Axboe
2011-03-30 11:20 ` Tejun Heo
2011-03-30 11:23 ` Jens Axboe
2011-03-30 11:21 ` Sergey Senozhatsky
2011-03-30 11:22 ` Jens Axboe
2011-03-30 11:49 ` Sergey Senozhatsky
2011-03-30 13:46 ` Vivek Goyal
2011-03-30 13:49 ` Tejun Heo
2011-03-30 14:01 ` Mike Snitzer
2011-03-30 14:27 ` Tejun Heo
2011-03-30 15:22 ` Vivek Goyal
2011-03-30 15:30 ` Tejun Heo
2011-03-30 17:13 ` Jens Axboe
2011-03-30 17:32 ` Tejun Heo
2011-03-30 17:56 ` Jeff Moyer
2011-03-30 18:12 ` Jens Axboe
2011-03-25 15:57 ` [OOPS] elevator private data for REQ_FLUSH Jens Axboe
2011-03-25 16:03 ` Markus Trippelsdorf
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