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

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Date:	Tue, 07 Feb 2012 08:43:50 +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 16:39 -0800, Tejun Heo wrote:
> Hello,
> 
> On Tue, Feb 07, 2012 at 08:31:22AM +0800, Shaohua Li wrote:
> > Since you are talking about performance, one of our microbenchmark (swap)
> > shows a regression. Alex bisect it to be b2efa05265d62bc2, which is related to
> > the ioc change. A little strange to me, don't expect such change can cause
> > performance issue. I haven't double check the issue, but if you have
> > ideas, please let me know.
> 
> Hmmm... I think the only thing which can be made slower by that patch
> is ioc release (ie. task exits).  What does the microbench do?
Quite simple, copy kernel source to tmpfs in tight memory environment.
This will trigger swap. The bisection result appears stable.

Thanks,
Shaohua

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