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

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Message-ID: <alpine.DEB.2.00.1105120938160.24560@router.home>
Date:	Thu, 12 May 2011 09:38:22 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Tejun Heo <tj@...nel.org>
cc:	Shaohua Li <shaohua.li@...el.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, eric.dumazet@...il.com,
	npiggin@...nel.dk
Subject: Re: [patch v2 0/5] percpu_counter: bug fix and enhancement

On Wed, 11 May 2011, Tejun Heo wrote:

> 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.  :-(

Same here.

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