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

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Date:	Mon, 21 Nov 2011 15:17:59 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.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>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 5/8] readahead: add /debug/readahead/stats

> +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.

-Andi
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