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

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Message-ID: <20110413031130.GH16342@mtj.dyndns.org>
Date:	Wed, 13 Apr 2011 12:11:30 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Shaohua Li <shaohua.li@...el.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"cl@...ux.com" <cl@...ux.com>
Subject: Re: [PATCH 4/4]percpu_counter: use atomic64 for counter

Hello,

On Wed, Apr 13, 2011 at 09:17:08AM +0800, Shaohua Li wrote:
> yes, we do have something this matters. the vm_committed_as
> percpu_counter could heavily contend the lock. please see
> http://marc.info/?l=linux-kernel&m=130144786026044&w=2
> We should fix vm_committed_as, but the atomic method also gives me very
> good output. When I do mmap/munmap test in a 24 CPU system, the atomic
> method gives me 50x faster.

That's good to hear.  Care to provide the performance info in the
commit message too?

Thanks.

-- 
tejun
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