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Date: Thu, 20 Feb 2003 15:05:59 +0100
From: Dejan Muhamedagic <dejan@hello-penguin.com>
To: Rik van Riel <riel@imladris.surriel.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: vm issues on sap app server
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Rik,

On Thu, Feb 20, 2003 at 10:21:50AM -0300, Rik van Riel wrote:
> On Thu, 20 Feb 2003, Dejan Muhamedagic wrote:
> 
> > # mem | grep Cache
> > Cached:        4569128 kB
> > SwapCached:     829668 kB
> > ActiveCache:    136728 kB
> 
> The "problem" here is that a lot of the memory in Cached: is
> mapped into process address space, so in effect it is process
> memory.
> 
> This is especially true for executables, libraries and shared
> memory segments, which you REALLY want to have treated as process
> memory and not as cache...
> 
> This makes the Cached statistic a bit confusing for administrators.

Is there a way to split the statistics?  It also sounds confusing :)

> > > In that case you're probably familiar with the cache size
> > > tuning, since AIX has the exact same tuning knob as rmap ;)
> >
> > AIX vmtune -P is equivalent to the Linux cache-max, but cache-max
> > is not implemented.
> 
> Doesn't it also have something like the borrow percentage, above
> which AIX will only reclaim from the cache, unless the repaging
> rate of the cache is higher than that of process memory ?

No, not that I'm aware of.  You can check the man page for vmtune
yourself:

http://publibn.boulder.ibm.com/doc_link/en_US/a_doc_lib/cmds/aixcmds6/vmtune.htm

BTW, there is also quite a bit of interesting documentation about
the AIX VMM.

Cheers!

Dejan
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