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Re: [Xen-devel] [Q] about Credit Scheduler Dom0 Scheduling policy.

On Wed, Oct 18, 2006 at 08:49:51PM +0900, Atsushi SAKAI wrote:
> My Test Configuration is
> #pcpu=1
> #vcpu=1(Dom0, DomU1, DomU2, DomU3)
> CPU intensive domain: DomU1 and DomU2
> I/O intensive domain: DomU3
> Privileged Domain   : Dom0 
> CPU intensive domain runs cpu-loop
> like follows,
> main(){int a;while(1){a++;};}
> I/O intensive domain runs fsdisk
> (which is included in unixbench 4.1.0)
> Privileged Domain runs
> xenmon.py or 
> xentrace in standard configuration(uses tools/xentrace/formats)
> The xentrace output is included in this mail.
> (I picked up the problem from xentrace outputs.)
> =============================================================

How much CPU resources are being consumed by all your
domains as reported by xentop?

If DomU1 and DomU2 are CPU bound, and DomU3 and Dom0 are
cooperatively doing I/O work with minimal CPU usage, one
would expect DomU3 and Dom0 to preempt both U1 and U2
when they become runnable.

When you say dom0 sometimes takes 60ms to run, how often
is that compared to the number of times it preempts and
immediately runs on the CPU?

If dom0 isn't preempting, in theory that is for one of
two reasons:
1- It's consumed its fair share of CPU already.
2- It's been inactive for a while.

Is this having a noticeable effect with credit vs sedf
on fdisk performance when competing against your spinner

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