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RE: [Xen-devel] [PATCH] Make "xm mem-set" be lower bound on domX-min-mem

To: "Ewan Mellor" <ewan@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Make "xm mem-set" be lower bound on domX-min-mem
From: "Puthiyaparambil, Aravindh" <aravindh.puthiyaparambil@xxxxxxxxxx>
Date: Mon, 22 May 2006 18:15:14 -0400
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Ky Srinivasan <ksrinivasan@xxxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH] Make "xm mem-set" be lower bound on domX-min-mem
Sorry to bring this up again. I see that there is dom0-min-mem option in
xend-config. The only time it comes into play is when ballooning memory
away from Dom0 to be given to a DomU that is requesting memory. Xend
ensures that Dom0's memory does not fall below dom0-min-mem. Shouldn't
this option also be taken care of by higher level mgmt tools? If not,
shouldn't an "xm mem-set" on Dom0 also look at this value?


> -----Original Message-----
> From: Ewan Mellor [mailto:ewan@xxxxxxxxxxxxx]
> Sent: Friday, May 19, 2006 11:29 AM
> To: Puthiyaparambil, Aravindh
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Keir Fraser
> Subject: Re: [Xen-devel] [PATCH] Make "xm mem-set" be lower bound on
> On Fri, May 12, 2006 at 12:16:57PM -0400, Puthiyaparambil, Aravindh
> > This patch causes "xm mem-set" to be lower bound on domX-min-mem
> > in xend-config. Another configuration option called domU-min-mem has
> > been introduced, which works similarly to dom0-min-mem. This is
> > users from freezing the system when doing "xm mem-set" on very low
> > values like 32M.
> >
> > Signed-off-by: Aravindh Puthiyaparambil
> > <aravindh.puthiyaparambil@xxxxxxxxxx>
> >
> I'm not so sure about this one.  We've discussed this issue recently,
> there are a number of people (notably some of the guys at IBM) who
don't want
> this limit to be imposed by Xend.  If you have one VM that you know to
be safe
> in 16MB, say, then you either need to set domU-min-mem to 0, defeating
> point of having it, or you need to have a "force" flag to override
> domU-min-mem.  The latter option here was disliked, because it was
felt that
> tools for VM management would just end up using the force flag all the
> because they don't know what the domU-min-mem setting is, and again,
> would defeat the point.
> The min-mem value should be a per-VM setting rather than a Xend
setting, so
> the check belongs with the tool that's managing VMs for you.
> Ewan.

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