Re: [Xen-devel] Credit scheduler

[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 less 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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