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RE: [Xen-devel] [PATCH] linux/balloon:don't allow ballooningdowna domain

To: <dan.magenheimer@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] linux/balloon:don't allow ballooningdowna domain below a reasonable limit
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Fri, 02 May 2008 20:30:56 +0100
Cc: Ky Srinivasan <KSrinivasan@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, keir.fraser@xxxxxxxxxxxxx, garloff@xxxxxxx
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>>> "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> 05/01/08 2:00 AM >>>
>OK, I think I am understanding it a bit better:
>the max_pfn part is just adding in some "slop"
>which is a fraction of total main memory which
>is growing smaller (roughly logarithmically)
>as memory grows larger.  I'm still not sure about
>the magic values in MB2PAGES though... I'm guessing
>these were gathered somehow experimentally?

I have to defer to the original author here - Kurt?

>With the "divide result of your algorithm by two",
>I was able to get thirteen 512MB domains (idle
>for now) running on a 2GB system.

You mean ballooned-down domains, right? Perhaps using your
self-ballooning change? I have to admit I'm a little nervous
about attempting to overcommit memory in this way in a
production environment, but as long as this depends on a
decision of the operator it's certainly a good option to have.

Jan

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