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Re: [Xen-devel] [PATCH] Fix auto-ballooning of dom0 for HVM domains

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Fix auto-ballooning of dom0 for HVM domains
From: Ewan Mellor <ewan@xxxxxxxxxxxxx>
Date: Fri, 19 May 2006 16:15:05 +0100
Cc: Charles Coffing <ccoffing@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On Fri, May 19, 2006 at 12:23:59PM +0800, Jiang, Yunhong wrote:

> Hi, Charles
>       Just one suggestion, for  xen-hvm-auto-balloon.diff, how about
> change 
>              xc.domain_setmaxmem(self.domid, m)
> to 
>              xc.domain_setmaxmem(self.domid, self.info['memory'] * 1024)
> The maxmem would be used to check when guest try to increase memory.
> Also, does anyone know the what the BALLOON_OUT_SLACK on
> tools/python/xen/xend/balloon.py stands for? The comments said it is
> "physinfo details are rounded".

When you get the free memory from xc.physinfo(), it may report (for example)
100MB free when actually there are 99.9MB free.  It rounds up because you
are often just a few pages short of the value you expect, because there are
pages being used for the I/O shared rings, for example.  This means that when
deciding how much memory to balloon, we need to subtract 1MB.


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