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Re: [Xen-devel] Performance difference between Xen versions

To: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>

From: Keir Fraser <keir.xen@xxxxxxxxx>

Date: Mon, 02 May 2011 07:41:06 +0100

Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>

Delivery-date: Sun, 01 May 2011 23:42:14 -0700

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Thread-topic: [Xen-devel] Performance difference between Xen versions

On 02/05/2011 06:31, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> wrote: >>> Is there any easy explanation for this? Both Xen versions are from SLES >>> (SLES11 or SLES11 SP1). >> I think cpufreq handling was off by default in 3.3, and is on by >> default on 4.0. Try turning this off, or using the performance >> governor. > Jan, you got it! With cpufreq=none Xen 4.0 has more or less the same numbers > as 3.3. Now I wonder why the default is so much slower. I looks as if the > hypervisor would run at a lower speed. I can't believe it should behave like > that! It runs at lower frequency unless your test offers sufficient load over a long enough time period. Short microbenchmarks are probably finished before the frequency governor can react. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel

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