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Re: [Xen-devel] Credit scheduler

To: Atsushi SAKAI <sakaia@xxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Credit scheduler
From: pak333@xxxxxxxxxxx
Date: Wed, 27 Jun 2007 05:15:32 +0000
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Thanks for the explanation, i am not sure i understood it correctly.
 
 
when does softirq get set. So when softirq is set a processor enters the scheduler every 3 micro secs? where in the source code is this handled. please could you send me some pointers
 
thanks
-Prabha
 
 
 
 
-------------- Original message --------------
From: Atsushi SAKAI <sakaia@xxxxxxxxxxxxxx>

> Hi, Prabha
>
>  30msec is the maximum time slice.
> And I guess your 3 microsecond is the response after
> SCHEDULE_SOFTIRQ is set.
> As you know,
> If SCHEDULE_SOFTIRQ is set,
> it waits softirq calls schedule(). (this time interval is 3microsec)
>
> And I/O intensive has higher priority than CPU intensive.
> So I/O intensive job is first dispatched domain in runq.
> This is because latency improvement for I/O intensive guest.
>
> So your behavior is not strange.
>
> Thanks
> Atsushi SAKAI
>
>
> pak333@xxxxxxxxxxx wrote:
>
> > Hi
> >
> > I have noticed that VMs are typically spending 3 microsecs or les s before they
> are being prempted. I thought that the credit schduler time slice was 30 ms. I
> have 4 VMs running and they are all cpu intensive except for 1 (which is IO
> intensive) but having a VM spend max 3 micro secs before being kicked out seems
> strange.
> >
> > Is there something else going on that i am not aware of. Is the time slice
> really 30 millisecs? I am using default parameters of the credit scheduler.
> >
> > Thanks
> > -Prabha
>
>
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