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Re: [Xen-devel] Error restoring DomU when using GPLPV

To: ANNIE LI <annie.li@xxxxxxxxxx>, James Harper <james.harper@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Error restoring DomU when using GPLPV
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 20 Aug 2009 13:28:01 +0100
Cc: Joshua West <jwest@xxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On 20/08/2009 12:55, "ANNIE LI" <annie.li@xxxxxxxxxx> wrote:

>> Just finished test,  live migration works well on winpv domu after
>> ballooning down those pages when pv driver first load.
> After more test, i find there are some problem with this method:
> ballooning down those pages when pv driver first load.
> If i balloon down those pages when driver first load, save/restore can
> only work only once, and the migration can not work.

Oh dear.

> It seems that a 
> restored vm lost those pages ballooned down. For migration, destination
> does not have those pages which ballooned down on source.

Right, that's the correct behaviour isn't it? Pages freed on source VM do
not magically reappear on destination VM?

> But if i balloon down those pages every time(not driver first load),  i
> tested save/restore/migration for several times, and all work fine.  But
> the domu will waste lots of memory in this situation.

Yes, that's weird. Do you know what condition causes guest memory allocation
failure on xc_domain_restore? Is it due to hitting the guest maxmem limit in
Xen? If so, is maxmem the same value across multiple iterations of
save/restore or migration?

> I will do more test about this and update here.


 -- Keir

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