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

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Message-Id: <20090428183237.EBDE.A69D9226@jp.fujitsu.com>
Date:	Tue, 28 Apr 2009 18:34:36 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	kosaki.motohiro@...fujitsu.com,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andi Kleen <andi@...stfloor.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Fr馘駻ic Weisbecker 
	<fweisbec@...il.com>, Larry Woodman <lwoodman@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.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

> 
> * Pekka Enberg <penberg@...helsinki.fi> wrote:
> 
> > I have no idea how expensive tracepoints are but I suspect they 
> > don't make too much sense for this particular scenario. After all, 
> > kmemtrace is mainly interested in _allocation patterns_ whereas 
> > this patch seems to be more interested in "memory layout" type of 
> > things.
> 
> My point is that the allocation patterns can be derived from dynamic 
> events. We can build a map of everything if we know all the events 
> that led up to it. Doing:
> 
>   echo 3 > /proc/sys/vm/drop_caches
> 
> will clear 99% of the memory allocations, so we can build a new map 
> from scratch just about anytime. (and if boot allocations are 
> interesting they can be traced too)
> 
> _And_ via this angle we'll also have access to the dynamic events, 
> in a different 'view' of the same tracepoints - which is obviously 
> very useful for different purposes.

I am one of most strongly want guys to MM tracepoint.
but No, many cunstomer never permit to use drop_caches.

I believe this patch and tracepoint are _both_ necessary and useful.



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