ways to help improve network performance

[Shaun Reitan]

I'm looking for any bit of info that any of you may have to help improve
performance to Dom0/U's.  Performance is fine as long as the host doesnt
have much going on but if you have a few domU's eating a good amount of
resources it will cause the latency to go up.  Right now i'm seeing a
30-60ms increase in latency. Host is a Dual Xeon with HT disabled.  Dom0 is
assigned both cpu's while domU's are given 1 cpu and distributed evenly
between cpu 0 and 1.


--

~Shaun




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[buw20031220]

Did you try a pci passthrough of the Networking cards.
Usually these servers are having dual nics at least. You leave one for dom0 and
another one is being passed to the most time-critical domU ?
Winfried

Zitat von Shaun <[hidden email]>:

> I'm looking for any bit of info that any of you may have to help improve
> performance to Dom0/U's.  Performance is fine as long as the host doesnt
> have much going on but if you have a few domU's eating a good amount of
> resources it will cause the latency to go up.  Right now i'm seeing a
> 30-60ms increase in latency. Host is a Dual Xeon with HT disabled.  Dom0 is
> assigned both cpu's while domU's are given 1 cpu and distributed evenly
> between cpu 0 and 1.
>

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[Pasi Kärkkäinen]

On Thu, Jun 01, 2006 at 02:21:27AM -0700, Shaun wrote:
> I'm looking for any bit of info that any of you may have to help improve
> performance to Dom0/U's.  Performance is fine as long as the host doesnt
> have much going on but if you have a few domU's eating a good amount of
> resources it will cause the latency to go up.  Right now i'm seeing a
> 30-60ms increase in latency. Host is a Dual Xeon with HT disabled.  Dom0 is
> assigned both cpu's while domU's are given 1 cpu and distributed evenly
> between cpu 0 and 1.
>

I did these steps to improve network performance with xen 3:

1. Assigned one CPU (hyperthread) _only_ for dom0
2. Changed the (default) xen scheduler to BVT
3. Changed the default linux io elevators from anticipatory -> cfq

-- Pasi

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[Shaun Reitan]

> 1. Assigned one CPU (hyperthread) _only_ for dom0

I did this with my initial testing but in the end i disabled HT because i
was told it would hurt performance.  Somthing about each HT shares the same
cache.  Anybody have more info on this?

> 2. Changed the (default) xen scheduler to BVT

Can this only be done by adding sched=bvt to the boot option or can it be
done some how on a live running host?

> 3. Changed the default linux io elevators from anticipatory -> cfq

when you build dom0 and domU did you set both to cfq or just domU?

~Shaun


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