linux-kernel - Re: [patch 10/20] SEQ replacement for anonymous pages

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Message-Id: <20071220082806.6F68.KOSAKI.MOTOHIRO@jp.fujitsu.com>
Date:	Thu, 20 Dec 2007 11:04:21 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Lee Schermerhorn <Lee.Schermerhorn@...com>
Subject: Re: [patch 10/20] SEQ replacement for anonymous pages

Hi Rik-san

> > > To keep the maximum amount of necessary work reasonable, we scale the
> > > active to inactive ratio with the size of memory, using the formula
> > > active:inactive ratio = sqrt(memory in GB * 10).
> 
> > why do you think best formula is sqrt(GB*10)?
> > please tell me if you don't mind.
> 
> On a 1GB system, this leads to a ratio of 3 active anon
> pages to 1 inactive anon page, and a maximum inactive
> anon list size of 250MB.
>  
> On a 1TB system, this leads to a ratio of 100 active anon
> pages to 1 inactive anon page, and a maximum inactive
> anon list size of 10GB.
> 
> The numbers in-between looked reasonable :)

thanks for your kind description.
I think it make sense.

and, please add comment liked blow table if you don't mind.
for take more intuitive description.

total     return    max 
memory    value     inactive anon
-------------------------------------
 10MB       1         5MB
100MB       1        50MB
  1GB       3       250MB
 10GB      10       0.9GB
100GB      31         3GB
  1TB     101        10GB
 10TB     320        32GB


> Basically the requirement is that the inactive anon list 
> is large enough that pages get a chance to be referenced
> again, but small enough that the maximum amount of work
> the VM needs to do is bounded to something reasonable.
> 
> > and i have a bit worry to it works well or not on small systems.
> > because it is indicate 1:1 ratio on less than 100MB memory system.
> > Do you think this viewpoint?
> 
> A 1:1 ratio simply means that the inactive anon list is
> the same size as the active anon list. Page replacement
> should still work fine that way.

I'm sold. thanks.


/kosaki



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