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

[Atsushi SAKAI <sakaia@xxxxxxxxxxxxxx>]

Hi, Emmanuel 

Thank you for your comments.

To be crealify, I am doing  unix bench 4.1.0 w_test@fsdisk/fsbuffer/fstime
with adding fsync().

(N.B.)I change the measurement configuration from file to physical disk.
Since previously I just want to show the blocking effect by xentrace.
Of course, other configuration are same.

The results are follows,
              credit credit(dom0weightx3)     sedf
fsbuffer(256)    16        16              33
fstime(1024)     66        66             133
fsdisk(4096)    266       266             266

unit:KBps
()means block size.

N.B. Dom0 Weight is added to 3times, since it equals other domain weight.
Dom0:U1:U2:U3=0.1:49.9:49.9:0.1 for Credit Dom0 Weightx3(768)
              0.1:49.9:49.9:0.1 for Credit Dom0 Weight=256
              0.9:48.7:48.7:0.8 for SEDF

I think blocking effect by CPU SPIN Domain should be considered.


And I think the reason is the 2 of your suggestion.

In my guess,
The credit scheduler runq has 2 priority.
If DomU1/2 are OVER running credit, no problem at all.
But DomU1/2 are UNDER running credit, the priorities are same as Dom0/U3.
So Dom0/U3 running is blocked by DomU1/2.

And weight seems no effect under this condition.
I guess credit_xtra makes inactivate the Dom0/U1 weight.


For including files
  For xentrace log, output size is huge 10lines/KB.
  I just included 100 line.


Thanks,
Atsushi SAKAI



>On Wed, Oct 18, 2006 at 02:11:15PM +0100, Emmanuel Ackaouy wrote:
>> 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.
>
>I should add that if (1), then increasing the weight of dom0
>should solve the problem. Try doubling it.
>
>If (2), then I'd like to see the xentrace output for a few
>seconds worth of running your workload.
>
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Attachment: sched-credit-trace.log
Description: Binary data

Attachment: sched-sedf-trace.log
Description: Binary data

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