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Re: [Xen-devel] Credit scheduler and latencies

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Milan Holzäpfel <listen@xxxxxxxx>
  • Date: Thu, 14 Dec 2006 18:48:51 +0100
  • Delivery-date: Thu, 14 Dec 2006 09:48:50 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

On Thu, 14 Dec 2006 18:24:43 +0100
Milan Holzäpfel <listen@xxxxxxxx> wrote:

> As it seems, a domain/VCPU can in some cases use more than it's fair
> share of PCPU and still interrupt other VCPUs if it only sleeps
> frequently enough.
> If a domain/VCPU spins for a long enough amount of time, it does indeed
> not interrupt other VCPUs anymore, with direct effects upon the latency
> I measured.

Thinking about it once again, the problem I'm having with this
behaviour is that a domain can't do I/O with low latency (which
possibly wouldn't require much CPU time by itself) as soon as it starts
consuming lots of CPU time, e.g. because an archiving process has just

Maybe it would be better to always interrupt the currently running
domain for a limited amount of time when another domain receives I/O?

Yet, I think I would still need a smaller scheduler quantum...


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