linux-kernel - Re: [PATCH 5/8] readahead: add /debug/readahead/stats

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Message-ID: <20111122141420.GA29261@localhost>
Date:	Tue, 22 Nov 2011 22:14:20 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Jens Axboe <jens.axboe@...cle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/8] readahead: add /debug/readahead/stats

Andi,

On Mon, Nov 21, 2011 at 10:17:59PM +0800, Andi Kleen wrote:
> > +static unsigned long ra_stats[RA_PATTERN_MAX][RA_ACCOUNT_MAX];
> 
> Why not make it per cpu?  That should get the overhead down, probably
> even enough that it can be enabled by default.
> 
> BTW I have an older framework to make it really easy to add per
> cpu stats counters to debugfs. Will repost, that would simplify
> it even more.

That's definitely a good facility to have. I would be happy to become
its first user :)

Thanks,
Fengguang
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