linux-kernel - Re: [patch v2 0/5] percpu_counter: bug fix and enhancement

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Message-ID: <20110511092848.GE1661@htj.dyndns.org>
Date:	Wed, 11 May 2011 11:28:48 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Shaohua Li <shaohua.li@...el.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	eric.dumazet@...il.com, cl@...ux.com, npiggin@...nel.dk
Subject: Re: [patch v2 0/5] percpu_counter: bug fix and enhancement

Hey, Shaohua.

On Wed, May 11, 2011 at 04:10:12PM +0800, Shaohua Li wrote:
> The new implementation uses lglock to protect percpu data. Each cpu has its
> private lock while other cpu doesn't take. In this way _add doesn't need take
> global lock anymore and remove the deviation. This still gives me about
> about 5x ~ 6x faster (not that faster than the original 7x faster, but still
> good) with the workload mentioned in patch 4.

I'm afraid I'm not too thrilled about lglock + atomic64 usage.  It is
a very patchy approach which addresses a very specific use case which
might just need a higher @batch.  I just can't see enough benefits to
justify the overhead and complexity.  :-(

Thanks.

-- 
tejun
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