linux-kernel - Re: [patch v2 4/4] percpu_counter: use atomic64 for counter

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Message-ID: <20110413190747.GE3987@mtj.dyndns.org>
Date:	Thu, 14 Apr 2011 04:07:47 +0900
From:	Tejun Heo <tj@...nel.org>
To:	shaohua.li@...el.com
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	cl@...ux.com, eric.dumazet@...il.com
Subject: Re: [patch v2 4/4] percpu_counter: use atomic64 for counter

On Wed, Apr 13, 2011 at 03:57:19PM +0800, shaohua.li@...el.com wrote:
> This can improve some workloads with percpu_counter->lock heavily contented.
> For example, vm_committed_as sometimes causes the contention. We should tune
> the batch count, but if we can make percpu_counter better, why not? In a 24
> CPUs system, 24 processes run stress mmap()/mmunmap(), the atomic method
> gives 50x faster.

Christoph already raised the issue but I'd also love to know a bit
more detail on the test than "50x faster".

Thanks.

-- 
tejun
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