linux-kernel - Re: [PATCH 5/7] mm: rework reclaim

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Message-Id: <20120302170328.37f42337.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 2 Mar 2012 17:03:28 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <jweiner@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/7] mm: rework reclaim_stat counters

On Fri, 02 Mar 2012 10:11:18 +0400
Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:

> KAMEZAWA Hiroyuki wrote:
> > On Wed, 29 Feb 2012 13:15:56 +0400
> > Konstantin Khlebnikov<khlebnikov@...nvz.org>  wrote:
> >
> >> Currently there is two types of reclaim-stat counters:
> >> recent_scanned (pages picked from from lru),
> >> recent_rotated (pages putted back to active lru).
> >> Reclaimer uses ratio recent_rotated / recent_scanned
> >> for balancing pressure between file and anon pages.
> >>
> >> But if we pick page from lru we can either reclaim it or put it back to lru, thus:
> >> recent_scanned == recent_rotated[inactive] + recent_rotated[active] + reclaimed
> >> This can be called "The Law of Conservation of Memory" =)
> >>
> > I'm sorry....where is the count for active->incative ?
> 
> If reclaimer deactivates page it will bump recent_rotated[LRU_INACTIVE_ANON/FILE],
> (if I understand your question right) recent_rotated[] now count each evictable lru independently
> 

Hm, then

	active -> active   : recent_rotated[active]   += 1 
	active -> inactive : recent_rotated[inacitve] += 1
	inactive->inactive : recent_rotated[inactive] += 1
	inactive->active   : recent_rotated[active]   += 1 ?

Ok, it seems rotated[active] + rotated[inactive] == scan.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

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