From: Gerd Hoffmann <kraxel@redhat.com>
To: Stefan <kvm@pms.ifi.lmu.de>
Cc: kvm@vger.kernel.org
Subject: Re: 64 bit guest much faster ?
Date: Mon, 26 Oct 2009 09:58:46 +0100 [thread overview]
Message-ID: <4AE564C6.3040605@redhat.com> (raw)
In-Reply-To: <4AE1D1A4.6050001@pms.ifi.lmu.de>
On 10/23/09 17:54, Stefan wrote:
>
> Hello,
>
> I have a simple question (sorry I'm a kvm beginner):
> Is it right that a 64bit guest (8 CPUs, 16GB) is
> much faster than a 32bit guest (8 CPUs, 16GB PAE).
^^^^
Yes. With *that* much memory the 32bit guest struggles with address
space limitations (32bit -> 4G), whereas the 64bit guest doesn't.
With up to 1G you shouldn't see a noticable difference. But the more
highmem the 32bit guest uses the higher is the penalty. Especially
without ept/npt as every kmap() of a high page is a roundtrip to the
hypervisor then.
cheers,
Gerd
next prev parent reply other threads:[~2009-10-26 8:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-23 15:54 64 bit guest much faster ? Stefan
2009-10-25 5:41 ` Avi Kivity
2009-10-26 8:58 ` Gerd Hoffmann [this message]
2009-10-26 10:12 ` Avi Kivity
2009-10-26 10:42 ` Michael Tokarev
2009-10-26 10:44 ` Avi Kivity
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