From: Avi Kivity <avi@redhat.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: mtosatti@redhat.com, kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: emulator: do not needlesly sync registers from emulator ctxt to vcpu
Date: Wed, 30 Mar 2011 15:41:09 +0200 [thread overview]
Message-ID: <4D9332F5.1060208@redhat.com> (raw)
In-Reply-To: <20110330133613.GZ7766@redhat.com>
On 03/30/2011 03:36 PM, Gleb Natapov wrote:
> >
> > It's wierd. Do you get perf hits in the copying?
> >
> How can I check. The memcpy is inlined.
>
perf annotate x86_emulate_instruction
(newer perf allows you to get there interactively from 'perf report')
> > Copying a couple of hot cache lines shouldn't take any measurable
> > time compared to a heavyweight exit.
> >
> The whole function takes only 1.5% CPU. Perf measures how much this
> function become faster and heavyweight exit is not part of the function.
It's still relative to exit cost. If the total exit was 2 us, then a 1%
decrease in cost translates to 40 ns.
(well, that's not unlikely for a 256 byte memcpy, but let's be sure).
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-03-30 13:41 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-29 12:08 [PATCH] KVM: emulator: do not needlesly sync registers from emulator ctxt to vcpu Gleb Natapov
2011-03-30 10:38 ` Avi Kivity
2011-03-30 10:47 ` Gleb Natapov
2011-03-30 10:50 ` Avi Kivity
2011-03-30 11:22 ` Gleb Natapov
2011-03-30 11:43 ` Gleb Natapov
2011-03-30 12:12 ` Avi Kivity
2011-03-30 12:12 ` Avi Kivity
2011-03-30 12:17 ` Avi Kivity
2011-03-30 12:48 ` Gleb Natapov
2011-03-30 13:26 ` Gleb Natapov
2011-03-30 13:29 ` Avi Kivity
2011-03-30 13:36 ` Gleb Natapov
2011-03-30 13:41 ` Avi Kivity [this message]
2011-03-30 13:43 ` Gleb Natapov
2011-03-30 13:46 ` Avi Kivity
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