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Message-Id: <20100405161110.6a66bf82.akpm@linux-foundation.org>
Date: Mon, 5 Apr 2010 16:11:10 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Dan Magenheimer <dan.magenheimer@...cle.com>
Cc: Avi Kivity <avi@...hat.com>, Jeremy Fitzhardinge <jeremy@...p.org>,
Dmitry Torokhov <dtor@...are.com>,
linux-kernel@...r.kernel.org, pv-drivers@...are.com
Subject: Re: [PATCH] VMware Balloon driver
On Mon, 5 Apr 2010 16:03:48 -0700 (PDT)
Dan Magenheimer <dan.magenheimer@...cle.com> wrote:
> > > On 04/06/2010 01:17 AM, Andrew Morton wrote:
> > > >> The basic idea of the driver is to allow a guest system to give up
> > > >> memory it isn't using so it can be reused by other virtual
> > machines (or
> > > >> the host itself).
> > > >>
> > > > So... does this differ in any fundamental way from what
> > hibernation
> > > > does, via shrink_all_memory()?
> > > >
> > >
> > > Just the _all_ bit, and the fact that we need to report the freed
> > page
> > > numbers to the hypervisor.
> > >
> >
> > So... why not tweak that, rather than implementing some parallel
> > thing?
>
> I think Avi was being facetious ("_all_"). Hibernation assumes
> everything in the machine is going to stop for awhile. Ballooning
> assumes that the machine has lower memory need for awhile, but
> is otherwise fully operational.
shrink_all_memory() doesn't require that processes be stopped.
If the existing code doesn't exactly match virtualisation's
requirements, it can be changed.
> Think of it as hot-plug memory
> at a page granularity.
hotplug is different because it targets particular physical pages. For
this requirement any old page will do. Preferably one which won't be
needed soon, yes?
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