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Date: Fri, 4 Nov 2016 18:39:18 +0100
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
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	<20161104170750.GA4346@amt.cnet>
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Subject: Re: [Qemu-devel] [QEMU PATCH] kvmclock: advance clock by time
 window between vm_stop and pre_save
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To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: kvm@vger.kernel.org, qemu-devel <qemu-devel@nongnu.org>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Juan Quintela <quintela@redhat.com>, Eduardo Habkost <ehabkost@redhat.com>

2016-11-04 15:07-0200, Marcelo Tosatti:
> On Fri, Nov 04, 2016 at 04:25:23PM +0100, Radim Kr=C4=8Dm=C3=A1=C5=99 w=
rote:
>> > +        /*
>> > +         * Transition from VM-running to VM-stopped via migration?
>> > +         * Record when the VM was stopped.
>> > +         */
>> > +
>> > +        if (state =3D=3D RUN_STATE_FINISH_MIGRATE &&
>> > +            !migration_in_postcopy(migrate_get_current())) {
>> > +            clock_gettime(CLOCK_MONOTONIC, &s->t_aftervmstop);
>>=20
>> How big (more like small) was the clock delta between here and
>> kvmclock_pre_save with postcopy?
>>=20
>> Thanks.
>=20
> qemu-system-x86_64: postcopy_ram_supported_by_host: userfaultfd not
> available: Function not implemented
>=20
> But should be about the same as precopy+this patch (guess as i don't=20
> know the postcopy path).

I was wondering about the improvement we could achieve by not excluding
postcopy from the time fixup.  (i.e. how much time elapses between
pausing and migrating the vm in postcopy)

I would also guess that it is not significant.