linux-ext4 - Re: [RFC, PATCH] Avoid hot statistics cache line in ext4 extent cache

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Date:	Fri, 13 Apr 2012 10:53:32 -0700
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, Ted Ts'o <tytso@....edu>,
	Vivek Haldar <haldar@...gle.com>,
	Andreas Dilger <adilger@...ger.ca>, linux-ext4@...r.kernel.org
Subject: Re: [RFC, PATCH] Avoid hot statistics cache line in ext4 extent
 cache

On Fri, 2012-04-13 at 10:42 -0700, Linus Torvalds wrote:
> On Wed, Apr 11, 2012 at 9:59 AM, Andi Kleen <andi@...stfloor.org> wrote:
> >
> > Ping. This scalability problem is still in 3.4-rc* and causes
> > major slowdowns.
> 
> Do you have numbers?
> 

In a benchmark that does mmaped-read, there is a 28% speed up
after getting rid of the counters.

> > Can we please revert fix it or revert
> > 556b27abf73833923d5cd4be80006292e1b31662 before release.
> 
> That commit ID doesn't make any sense, and doesn't seem to have
> anything to do with any statistics counters that your email talks
> about. So regardless, you'd need to explain why that commit causes the
> problems you talk about, I'm not going to revert a random commit that
> doesn't even look what you describe.
> 
> Ted?
> 
>                 Linus


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