From: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
To: Benjamin Prosnitz <b-prosnitz-angj7XTnwNpXfO9P/gJGhg@public.gmane.org>
Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: Floating point vs Integer performance
Date: Tue, 13 Mar 2007 10:03:20 +0200 [thread overview]
Message-ID: <45F65AC8.2000605@qumranet.com> (raw)
In-Reply-To: <1173730724.7220.5.camel@localhost>
Benjamin Prosnitz wrote:
> I ran some benchmarks inside of KVM-12 on my system and outside of KVM
> (no virtualization on my system). I found that floating point
> performance when running both with and without KVM was approximately the
> same, but integer performance in KVM was about 25% of what I get when
> running the test outside of KVM. These were tests using Dhrystone 2 and
> Double Precision Whetstone on a Core 2 Duo T7200 processor.
>
> Any thoughts on why the integer and floating point performance appears
> to differ so much?
>
>
Perhaps the integer benchmarks thrash the mmu cache. Try raising
KVM_NUM_MMU_PAGES to 1024.
4MB per VM lowmem is a lot, but if it helps many workloads, it's worth it.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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next prev parent reply other threads:[~2007-03-13 8:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-12 20:18 Floating point vs Integer performance Benjamin Prosnitz
2007-03-13 8:03 ` Avi Kivity [this message]
2007-03-13 8:16 ` Michael Riepe
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