Re: [Xen-devel] Poor performance with Linux 3.x as dom0

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-05-02 at 14:11 +0100, Andreas Kinzler wrote:
> Hello Jeremy + Konrad + all kernel devs,
> 
> while it is great to see that vanilla dom0 seems to work, the 
> performance breakdown compared to xenified 2.6.34 (from opensuse) is 
> huge. Here are my benchmarks:

There were a couple of performance fixes posted recently, one of them
was "xen: correctly check for pending events when restoring irq flags"
from David Vrabel, which is now in mainline as 7eb7ce4d2e89 and marked
for stable backport. The other was something to do with blk i/o
performance from Stefano Stabellini which I don't have a handy reference
too or status on (hopefully Konrad does though).

I think those will undoubtedly help although I think performance tuning
of the upstream dom0 kernel is still something we need to do more of in
the short term.

> Xen 4.1.1, Xeon E5620, Supermicro X8DTi-F, 12 GB RAM, dom0 2 VCPUs
> 
> time emerge apache:
> 
>               3.2.12-dom0     3.3.4-dom0      2.6.34.10-dom0
>       real    1m0.560s        0m59.971s       0m47.689s
>       user    0m40.939s       0m40.619s       0m41.355s
>       sys     0m18.865s       0m18.305s       0m11.441s
> 
> time make -j4 (3.2.12 linux compile):
> 
>               3.2.12-dom0     3.3.4-dom0      2.6.34.10-dom0
>       real    5m8.793s        5m4.888s        4m20.576s
>       user    8m1.746s        7m59.726s       7m10.375s
>       sys     1m39.010s       1m32.994s       0m56.304s

Did you happen to also compare 3.2.12 and 2.6.34.10 running these
workloads natively?

Ian.


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