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xen-devel
Re: [Xen-devel] More network tests with xenoprofile this time
To: |
William Cohen <wcohen@xxxxxxxxxx>, "Santos, Jose Renato G" <joserenato.santos@xxxxxx> |
Subject: |
Re: [Xen-devel] More network tests with xenoprofile this time |
From: |
Andrew Theurer <habanero@xxxxxxxxxx> |
Date: |
Wed, 8 Jun 2005 14:20:02 -0500 |
Cc: |
Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, Aravind Menon <aravind.menon@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, G John Janakiraman <john@xxxxxxxxxxxxxxxxxxx>, "Turner, Yoshio" <yoshio_turner@xxxxxx> |
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> Hi Renato,
>
> The article was an interesting application of the xenoprof.
>
> It seem like it would be useful to also have data collected using the
> cycle counts (GLOBAL_POWER_EVENTS on P4) to give some indication of
> areas with high overhead operations. There may be some areas with few
> very expensive instructions. Calling attention to those areas would
> help improve performance.
>
> The increases in I-TLB and D-TLB events for Xen-domain0 shown in
> Figure 4 are surprising. Why would the working sets be that much
> larger for Xen-domain0 than regular linux, particularly for code? Is
> there an table similar to table 3 for I-TLB event sample locations?
>
> Can't the VMM use a 4-MB page and the Xen-domain0 kernel shouldn't be
> that much larger than regular linux kernel? How were TLB flushes
> ruled out as a cause? Could the PERFCOUNTER_CPU counters in
> perfc_defn.h be used to see if the VMM is doing a lot of TLB flushes?
I had the same concern as you, and IMO, it seemed unlikely that the
working set for dom0 would be so much larger to cause significant
amount of TLB miss. I also suspect TLB flushes to be the problem, but
I have not had a chance to look at it. I hope to very soon.
-Andrew
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