From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH] KVM: emulator: do not needlesly sync registers from
 emulator ctxt to vcpu
Date: Wed, 30 Mar 2011 14:48:28 +0200
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To: Avi Kivity <avi@redhat.com>
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On Wed, Mar 30, 2011 at 02:17:55PM +0200, Avi Kivity wrote:
> On 03/30/2011 01:43 PM, Gleb Natapov wrote:
> >After reboot perf started to work. I ran modified emulator.flat unit
> >test. It was modified to run test_cmps() in an endless loop.
> >
> >Without patch:
> >1.71%  qemu-system-x86  [kvm]                 [k] x86_emulate_instruction
> >1.51%  qemu-system-x86  [kvm]                 [k] x86_emulate_instruction
> >1.68%  qemu-system-x86  [kvm]                 [k] x86_emulate_instruction
> >
> >With patch:
> >0.84%  qemu-system-x86  [kvm]                 [k] x86_emulate_instruction
> >0.96%  qemu-system-x86  [kvm]                 [k] x86_emulate_instruction
> >0.89%  qemu-system-x86  [kvm]                 [k] x86_emulate_instruction
> >
> 
> The cause might be kvm_rip_write() using vmwrite.  Can you use perf
> to see where the hits are in x86_emulate_instruction?
> 
> If that's the case, we may be able to do local optimizations to
> kvm_rip_write(), kvm_set_rflags(), and toggle_interruptiblity()
> instead of this global change.
> 
I can leave copying there and eliminate only kvm_rip_write and see
perf data.

--
			Gleb.