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Re: [Xen-devel] Re: Poor performance on HVM (kernbench)

  • To: "Anthony Liguori" <anthony@xxxxxxxxxxxxx>
  • From: "George Dunlap" <George.Dunlap@xxxxxxxxxxxxx>
  • Date: Thu, 11 Sep 2008 10:35:42 +0100
  • Cc: Muli Ben-Yehuda <MULI@xxxxxxxxxx>, deshantm@xxxxxxxxx, Anthony Liguori <aliguori@xxxxxxxxxx>, xen-devel mailing list <xen-devel@xxxxxxxxxxxxxxxxxxx>, Marcelo Tosatti <mtosatti@xxxxxxxxxx>
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On Wed, Sep 10, 2008 at 11:42 PM, Anthony Liguori <anthony@xxxxxxxxxxxxx> wrote:
>> Xen 3.3 should be an improvement with shadow3 right?
> I know it is for Windows, but there's always the possibility that it has
> caused a regression in Linux performance.

Shadow3 was definitely developed with Windows in mind.  Since it makes
shadows act more like a hardware TLB, I'd expect it to perform better,
or at least no worse; but since that's the biggest change with Xen HVM
between 3.2 and 3.3, that's the first place I'd look.

Todd,  would it be possible to send me a 30-second xentrace "sample"
of kernbench running under 3.2 and 3.3?  The relevant command:

xentrace -S 256 -e all /tmp/[filename].trace

Set the kernbench run going in the guest, let it get going for about
30 seconds or so, and then start xentrace.  Let it run for 30 seconds,
then kill it.  In 3.3, you can use the -T parameter to have it stop
after 30 seconds; in 3.2, you can do something like:

xentrace -S 256 -e all /tmp/[filename].trace & sleep 30 ; killall -INT xentrace

You can send me the files via something like http://yousendit.com.

If you could possibly take a trace with a recent xen-unstable build,
that would be even more helpful, since there are some key xentrace
changes that make the information even more useful.


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