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

To: deshantm@xxxxxxxxx
Subject: Re: [Xen-devel] Re: Poor performance on HVM (kernbench)
From: Gianluca Guida <gianluca.guida@xxxxxxxxxxxxx>
Date: Thu, 11 Sep 2008 11:00:40 +0100
Cc: Muli Ben-Yehuda <MULI@xxxxxxxxxx>, Anthony Liguori <aliguori@xxxxxxxxxx>, xen-devel mailing list <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Todd Deshane wrote:
Xen 3.3 should be an improvement with shadow3 right?

As other people already said, shadow3 (especially the current unsync policy) was mostly developed with Windows performance in mind. I would be surprised if the shadow algorithm is causing such a performance loss though; but in any case, you can disable the out-of-sync feature by removing SHOPT_OUT_OF_SYNC from SHADOW_OPTIMIZATIONS in xen/arch/x86/mm/shadows/private.h (setting it to 0xff instead of 0x1ff), reverting the shadow code back to shadow 2 again.

Can you please test that and see if it makes any difference?

Thanks,
Gianluca


Should I need to adjust the shadow_memory parameter for the guest?

I'm going to try Xen 3.2.1 from source next.

Todd

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