From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
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, 07 Feb 2012 07:49:19 +0100 [thread overview]
Message-ID: <4F30C96F.1000905@kernel.dk> (raw)
In-Reply-To: <20120206215451.GD21292@google.com>
On 02/06/2012 10:54 PM, Tejun Heo wrote:
> put_io_context() performed a complex trylock dancing to avoid
> deferring ioc release to workqueue. It was also broken on UP because
> trylock was always assumed to succeed which resulted in unbalanced
> preemption count.
>
> While there are ways to fix the UP breakage, even the most
> pathological microbench (forced ioc allocation and tight fork/exit
> loop) fails to show any appreciable performance benefit of the
> optimization. Strip it out. If there turns out to be workloads which
> are affected by this change, simpler optimization from the discussion
> thread can be applied later.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> LKML-Reference: <1328514611.21268.66.camel@sli10-conroe>
> ---
> I couldn't find any statiscally meaningful advantage of the
> optimization with tight fork/exit tests w/ forced ioc creation on
> fork, which gotta be the most pathological test case for the code
> path. So, let's remove the ugly optimization. If I missed sth, we
> can resurrect the simpler optimization later. Jens, this is on top of
> linus#master without Shaohua's patch.
OK, then I'm fine with cleaning it up. Applied, thanks Tejun.
--
Jens Axboe
next prev parent reply other threads:[~2012-02-07 6:50 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 [this message]
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
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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