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From: Tejun Heo <tj@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>, Vivek Goyal <vgoyal@redhat.com>,
	Shaohua Li <vivek.goyal2008@gmail.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Knut Petersen <Knut_Petersen@t-online.de>,
	mroos@linux.ee
Subject: Re: [PATCH] block: strip out locking optimization in put_io_context()
Date: Tue, 7 Feb 2012 08:47:35 -0800	[thread overview]
Message-ID: <20120207164735.GH21292@google.com> (raw)
In-Reply-To: <CA+55aFxcjE4FsUVoarc+8OTi4OkqtgBmHq500=qaCeTqqWnqoA@mail.gmail.com>

Hello,

On Tue, Feb 07, 2012 at 08:33:15AM -0800, Linus Torvalds wrote:
> Yeah, please just get rid of the crazy code. Maybe *that* fixes the
> regression too, who knows?
> 
> For all we know, the "fast case" is what causes extra locking only to
> then fail and not even be a fast-path.

Yeah, I was about to ask Shaohua to test the version w/o optimization.
With heavily loaded request_queue, trylock failure could be frequent,
which I wasn't testing.

Shaohua, can you please test the version w/o optimization?  Also, can
you please give a bit more details on the setup?  Are there multiple
swap devices?  Is it SSD or rotating disk?

> I think our default action should always be to simplify and clean up
> code, unless you have seriously hard numbers to show that the code
> complexity is worth it.

Sure, it was originally all in put_io_context() and while moving
things to wq, it got progressively complex and I lost sense of
complexity from staring at it too long.

Thanks.

-- 
tejun

  reply	other threads:[~2012-02-07 16:47 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-06  7:50 [patch]block: fix ioc locking warning Shaohua Li
2012-02-06  7:55 ` Jens Axboe
2012-02-06 15:12 ` Vivek Goyal
2012-02-06 16:09   ` Jens Axboe
2012-02-06 16:37     ` Vivek Goyal
2012-02-06 16:44       ` Tejun Heo
2012-02-06 16:58         ` Linus Torvalds
2012-02-06 17:27           ` Tejun Heo
2012-02-06 20:16             ` Jens Axboe
2012-02-06 21:54               ` [PATCH] block: strip out locking optimization in put_io_context() Tejun Heo
2012-02-07  6:49                 ` Jens Axboe
2012-02-07 16:22                   ` Tejun Heo
2012-02-07 16:28                     ` Jens Axboe
2012-02-07 16:33                       ` Linus Torvalds
2012-02-07 16:47                         ` Tejun Heo [this message]
2012-02-07 17:17                           ` Tejun Heo
2012-02-08  0:19                           ` Shaohua Li
2012-02-08  8:29                             ` Shaohua Li
2012-02-08 16:29                               ` Tejun Heo
2012-02-08 16:34                                 ` Linus Torvalds
2012-02-08 16:49                                   ` Tejun Heo
2012-02-08 16:56                                     ` Tejun Heo
2012-02-08 17:23                                       ` Tejun Heo
2012-02-09  6:22                                 ` Shaohua Li
2012-02-09 17:59                                   ` Tejun Heo
2012-02-09 18:07                                     ` Linus Torvalds
2012-02-09 19:24                                       ` Tejun Heo
2012-02-09 23:48                                         ` Tejun Heo
2012-02-10  5:14                                           ` Shaohua Li
2012-02-10  8:48                                             ` Shaohua Li
2012-02-11  2:17                                               ` Tejun Heo
2012-02-11 11:35                                                 ` Jens Axboe
2012-02-13  1:34                                                 ` Shaohua Li
2012-02-13 20:49                                                   ` Tejun Heo
2012-02-14  2:36                                                     ` Shaohua Li
2012-02-14 16:39                                                       ` Tejun Heo
2012-02-10  3:09                                       ` Shaohua Li
2012-02-07 23:00                   ` [PATCH] block: fix lockdep warning on io_context release put_io_context() Tejun Heo
2012-02-06 20:36             ` [patch]block: fix ioc locking warning Tejun Heo
2012-02-07  0:31               ` Shaohua Li
2012-02-07  0:39                 ` Tejun Heo
2012-02-07  0:43                   ` Shaohua Li
2012-02-07  0:59                     ` Tejun Heo
2012-02-07  1:10                       ` Shaohua Li
2012-02-07  1:33                         ` Shaohua Li
2012-02-07  5:22                       ` Shaohua Li
2012-02-07 22:34                         ` Linus Torvalds
2012-02-06 16:22 ` Tejun Heo
2012-02-08 18:07 ` walt

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