From: Tejun Heo <tj@kernel.org>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Jeff Moyer <jmoyer@redhat.com>, Mike Snitzer <snitzer@redhat.com>,
Jens Axboe <axboe@kernel.dk>,
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 (was: Re: elevator private data for REQ_FLUSH)
Date: Wed, 30 Mar 2011 09:57:52 +0200 [thread overview]
Message-ID: <20110330075752.GC17523@htj.dyndns.org> (raw)
In-Reply-To: <20110330074123.GA17523@htj.dyndns.org>
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.
Thanks.
--
tejun
next prev parent reply other threads:[~2011-03-30 7:57 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 [this message]
2011-03-30 7:59 ` [PATCH] block: eliminate ELEVATOR_INSERT_REQUEUE Jens Axboe
2011-03-30 8:02 ` 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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