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Re: [Xen-devel] [Patch 0/6] xen: cpupool support

To: Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [Patch 0/6] xen: cpupool support
From: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Date: Tue, 21 Apr 2009 13:11:12 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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Thanks for doing this work.  Overall things look like they're going in
the right direction.

However, it's a pretty big change, and I'd like to hear some more
opinions.  So to facilitate discussion on the list, would you please
send out another e-mail with:
1. A description of the motivation for this work (the basic problem
you're trying to solve)
2. A description overall of what cpu pools does
3. A description of any quirky corner cases you ran into, how you
solved them, and why you chose the way you did

Here are some examples for #3 I got after spending a couple of hours
looking at your patch:
* The whole "cpu borrowing" thing
* Dealing with the idle domain
* Why the you expose allocating and freeing of vcpu and pcpu data in
the sched_ops structure

Some of these I'd people to be able to discuss who don't have the time
/ inclination to spend looking at the patch (which could use a lot
more comments).

As for me: I'm happy with the general idea of the patch (putting cpu
pools in underneath the scheduler, and allowing pools to have
different schedulers).  I think this is a good orthogonal to the new
scheduler.  I'm not too keen on the whole "cpu borrowing" thing; it
seems like there should be a cleaner solution to the problem.  Overall
the patches need more comments.  I have some coding specific comments,
but I'll save those until the high-level things have been discussed.


On Fri, Apr 17, 2009 at 12:54 PM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:
> On 17/04/2009 10:53, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> wrote:
>> as already proposed in January, we are now ready to post our patches for
>> support of cpupools.
> Thanks. I hope George can comment on these, as it makes sense to integrate
> this stuff into his overall scheduler2 work I think, rather than considering
> them for inclusion as a separate thing.
>  -- Keir
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