linux-kernel - Re: [PATCH -mm 1/2] irq_work, Use llist in irq

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Message-ID: <1314969972.1301.15.camel@twins>
Date:	Fri, 02 Sep 2011 15:26:12 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm 1/2] irq_work, Use llist in irq_work

On Fri, 2011-09-02 at 09:18 +0800, Huang Ying wrote:
> On 09/01/2011 06:00 PM, Peter Zijlstra wrote:
> > On Thu, 2011-09-01 at 16:44 +0800, Huang Ying wrote:
> > 
> >> Because llist is in library, it may be used in highly contended case and
> >> light/un-contended loads.  So maybe code as above is best choice for llist.
> > 
> > Well the thing is, if you're heavily contended you should probably be
> > doing something else..
> 
> So which solution is preferable?
> 
> 1) no cpu_relax
> 2) cpu_relax after first cmpxchg
> 
> Personally, I prefer 2).  It should have acceptable overhead in
> ligh/un-contended loads.  Do you agree.

I guess so, we can always poke at it again when someone finds something
to measure.
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