From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel@nongnu.org, kvm@vger.kernel.org,
Luiz Capitulino <lcapitulino@redhat.com>
Subject: Re: [Qemu-devel] [QEMU patch 2/2] kvm: allow configuration of tsc deadline timer advancement
Date: Wed, 10 Dec 2014 19:39:06 +0100 [thread overview]
Message-ID: <20141210183905.GA31236@potion.brq.redhat.com> (raw)
In-Reply-To: <5488892C.7010606@redhat.com>
2014-12-10 18:55+0100, Paolo Bonzini:
> Well, my preferred choice would be automatic adjustment with a module
> parameter. If we need manual tuning, per-CPU would be my choice, but
> automatic is nicer anyway. :)
I agree with Paolo, and think it would be better not to touch QEMU ...
it makes little sense to migrate this value and it is probably going to
be quite similar on every CPU, so a writeable module parameter is a
better starting point. (We can always turn it into a nightmare later.)
If you measure the difference between the TSC you wanted and got on VM
entry, you can use it to automatically guess a delta for the next timer.
(That is IMO exactly what you would do with a manual tuning.
The algorithm should probably prefer being a bit late than early too.)
next prev parent reply other threads:[~2014-12-10 18:39 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-10 16:23 [Qemu-devel] [QEMU patch 0/2] QEMU lapic tsc deadline advancement Marcelo Tosatti
2014-12-10 16:23 ` [Qemu-devel] [QEMU patch 1/2] kvm: sync kernel headers Marcelo Tosatti
2014-12-10 16:23 ` [Qemu-devel] [QEMU patch 2/2] kvm: allow configuration of tsc deadline timer advancement Marcelo Tosatti
2014-12-10 17:01 ` Paolo Bonzini
2014-12-10 17:04 ` Marcelo Tosatti
2014-12-10 17:09 ` Paolo Bonzini
2014-12-10 17:27 ` Marcelo Tosatti
2014-12-10 17:29 ` Paolo Bonzini
2014-12-10 17:35 ` Marcelo Tosatti
2014-12-10 17:55 ` Paolo Bonzini
2014-12-10 18:39 ` Radim Krčmář [this message]
2014-12-10 18:59 ` Paolo Bonzini
2014-12-10 17:06 ` Eric Blake
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