linux-kernel - Re: [patch]block: fix ioc locking warning

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Date:	Tue, 07 Feb 2012 09:10:20 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	lkml <linux-kernel@...r.kernel.org>,
	Knut Petersen <Knut_Petersen@...nline.de>, mroos@...ux.ee
Subject: Re: [patch]block: fix ioc locking warning

On Mon, 2012-02-06 at 16:59 -0800, Tejun Heo wrote:
> On Tue, Feb 07, 2012 at 08:43:50AM +0800, Shaohua Li wrote:
> > Quite simple, copy kernel source to tmpfs in tight memory environment.
> > This will trigger swap. The bisection result appears stable.
> 
> Looked through the commit again but it really doesn't change fast
> paths.  The only paths which can be slower are ioc and q exits.  Can
> you please do the followings?
> 
> * Share the script used for microbench.  Maybe it somehow exposes
>   slower exit path?  How much regression are we talking about?
I need strip the script out from our test framework, but it essentially
is a 'time copy -a tmpfs/kernelsource tmpfs/copy'. The time increased
~20% with 3.3-rc1.

> * Test with the this_q != locked_q trylock patch.
sure.

Thanks,
Shaohua

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