From: Junichi Nomura <j-nomura@ce.jp.nec.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
device-mapper development <dm-devel@redhat.com>,
Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH for-4.2 2/3] block, dm: don't copy bios for request clones
Date: Mon, 1 Jun 2015 01:14:26 +0000 [thread overview]
Message-ID: <556BB1F1.4030404@ce.jp.nec.com> (raw)
In-Reply-To: <20150529165451.GA2682@lst.de>
On 05/30/15 01:54, Christoph Hellwig wrote:
> On Thu, May 28, 2015 at 06:38:29AM +0000, Junichi Nomura wrote:
>> I'm also worried about partial completion case.
>> For successful partial completion, current code completes
>> bio before fully completing the request.
>> Your patch changes bios not completed until the request is
>> fully completed.
>
> Yes. Why are you worried about this case?
See below.
>> I'm not very sure how much impact does the removal of partial
>> completion have in the real world.
>> If partial completion is so negligible, I think it should be
>> handled in such a way all the cases, instead of special casing
>> REQ_CLONE.
>
> It isn't negligible - under load it actually does matter that
> we handle partial completions as arrays decide to just complete
> a request partially, so if we don't handle them we might end
> up in a loop not making progress.
OK.
> But if we only do that once on
> path fail over it's not an actual issue.
But with your patch, the fail over happens after full completion
of the request. Is it ok?
--
Jun'ichi Nomura, NEC Corporation
next prev parent reply other threads:[~2015-06-01 1:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-22 13:14 [PATCH for-4.2 1/3] block: remove management of bi_remaining when restoring original bi_end_io Mike Snitzer
2015-05-22 13:14 ` [PATCH for-4.2 2/3] block, dm: don't copy bios for request clones Mike Snitzer
2015-05-26 6:20 ` Junichi Nomura
2015-05-27 8:21 ` Christoph Hellwig
2015-05-27 9:50 ` Junichi Nomura
2015-05-28 6:38 ` Junichi Nomura
2015-05-29 16:54 ` Christoph Hellwig
2015-06-01 1:14 ` Junichi Nomura [this message]
2015-06-03 7:37 ` Christoph Hellwig
2015-06-03 23:13 ` Junichi Nomura
2015-05-29 16:55 ` Christoph Hellwig
2015-06-01 1:19 ` Junichi Nomura
2015-06-03 7:39 ` Christoph Hellwig
2015-05-22 13:14 ` [PATCH for-4.2 3/3] block: remove export for blk_queue_bio Mike Snitzer
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