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Re: [Xen-devel] RE: tmem - really default to on?

To: Jan Beulich <JBeulich@xxxxxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] RE: tmem - really default to on?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 09 Feb 2010 13:31:07 +0000
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Christian Limpach <Christian.Limpach@xxxxxxxxxxxxx>
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On 09/02/2010 13:00, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>> I think the correct approach to all of this is to move system-wide to
>> allocating memory in 2MB contiguous aligned chunks.  There's no sense in
>> doing guest allocations any finer-grained than that and there are
>> noticeable performance wins from all the superpage support that's gone
>> in recently.  Then little things like needing 16k contiguous areas just
>> go away.
> 
> I have to admit that I can't see how this would work with ballooning,
> or (if the balloon driver was adjusted to deal with this) with
> fragmentation inside Dom0 (or any other guest that memory is
> intended to be removed from). Nor am I sure tmem could be
> changed to deal with 2Mb chunks instead of 4k ones.

Balloon driver is the obvious fly in the ointment that I can see, too.

 -- Keir



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