linux-kernel - Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags

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Message-ID: <12c511ca0904281111r10f37a5coe5a2750f4dbfbcda@mail.gmail.com>
Date:	Tue, 28 Apr 2009 11:11:52 -0700
From:	Tony Luck <tony.luck@...il.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Larry Woodman <lwoodman@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Matt Mackall <mpm@...enic.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags

On Tue, Apr 28, 2009 at 1:33 AM, Wu Fengguang <fengguang.wu@...el.com> wrote:
> 1) FAST
>
> It takes merely 0.2s to scan 4GB pages:
>
>        ./page-types  0.02s user 0.20s system 99% cpu 0.216 total

OK on a tiny system ... but sounds painful on a big
server. 0.2s for 4G scales up to 3 minutes 25 seconds
on a 4TB system (4TB systems were being sold two
years ago ... so by now the high end will have moved
up to 8TB or perhaps 16TB).

Would the resulting output be anything but noise on
a big system (a *lot* of pages can change state in
3 minutes)?

-Tony
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