linux-kernel - Re: [PATCH 3/4] vmstat: add anon_scan

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Date:	Wed, 30 Dec 2009 22:13:42 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	kosaki.motohiro@...fujitsu.com,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 3/4] vmstat: add anon_scan_ratio field to zoneinfo

> * KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> [2009-12-28 16:48:51]:
> 
> > Vmscan folks was asked "why does my system makes so much swap-out?"
> > in lkml at several times.
> > At that time, I made the debug patch to show recent_anon_{scanned/rorated}
> > parameter at least three times.
> > 
> > Thus, its parameter should be showed on /proc/zoneinfo. It help
> > vmscan folks debugging.
> >
> 
> Hmmm.. I think this should come under DEBUG_VM, a lot of tools use
> /proc/zoneinfo, the additional overhead may be high.. no? Also,
> I would recommend adding the additional details to the end, so
> as to not break existing tools (specifically dump line # based
> tools).

Thanks, I have three answer. 1)  I really hope to don't enclose DEBUG_VM. otherwise 
my harm doesn't solve. 2) but your performance worry is fair enough. I plan to remove 
to grab zone->lru_lock in reading /proc/zoneinfo. 3)  append new line doesn't break 
existing tools. because zoneinfo show vmstat and we often append new vmstat in past 
years. but I haven't seen zoneinfo breakage bug report. because zoneinfo file show 
multiple zone information, then nobody access it by line number.





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