Re: [Xen-devel] Does Xen scheduler preserves 5% of its utilization to every VM?

[walmart <vmwalmart@xxxxxxxxx>]

Hi, George:

Thanks for your reply! I am using PV domains. Even if I am using the
default credit based scheduler, the same situation happens.

Please allow me to restate my situation:
Fedora 13, 64bit, compiled Xen 4.0.2 from source code. On a 4 core
machine, domain 0 is pinned to core 1.

I configured domain 1 to have 1 vcpu, and pinned it to core 1.

I am running a busy loop in domain 1.

The xm top in domain 0 shows domain 1 only get exactly 95% of the CPU.

I traced the data for 10 secs. (when only domain 1 was running,
occupying 95% of the cpu). using:
 xentrace -D -e 0x2f000 -S 256 -T 10 trace_credit_sched

I then traced the data for another 10 secs, with domain 1 and 2 both
running busy, occupying 50% of the cpu. using:
 xentrace -D -e 0x2f000 -S 256 -T 10 trace_credit_sched_both

But I don't know how to use xenalyze... Could you help me w/ the trace?

Thanks very much!

Best!

Sam


On Tue, Sep 14, 2010 at 4:14 AM, George Dunlap <dunlapg@xxxxxxxxx> wrote:
> Are these PV domains, or HVM domains?
>
> If they're HVM domains, by necessity they will be doing QEMU
> operations. ÂWhen doing qemu operations, they block and dom0 is
> scheduled. ÂThis blocking would allow the lower-priority VM space to
> run.
>
> Your best bet is to use xentrace + xenalyze to see what's going on
> with scheduling. ÂYou can find xenalyze here:
> Âhttp://xenbits.xensource.com/ext/xenalyze.hg
>
> Â-George
>
> On Tue, Sep 14, 2010 at 7:16 AM, walmart <vmwalmart@xxxxxxxxx> wrote:
>> Hi, all
>>
>> I was trying to write a Xen scheduler, it is a fixed priority one and
>> would give domain 1 higher priority than domain 2. (which means
>> whenever domain 1 is runnable, it got the cpu to run).
>>
>> I got two domains running. It is on Fedora 13, 64 bit, Xen 4.0.1.
>>
>> domain 1 and doman 2 both only have one vcpu, and are pinned to the same 
>> core.
>>
>> The strange thing is:
>>
>> domain 1 is busy, domain 2 is idle, domain 1 got 95% of the cpu;
>> domain 1 is idle, domain 2 is busy, domain 2 got 95% of the cpu;
>> domain 1 is busy, domain 2 is busy, domain 1 got 95% of the cpu, while
>> domain 2 got the remaining 5%.
>>
>> I checked the schedule() function again and again, still couldn't
>> figure out why would this happen.
>>
>> Could anyone give me some hint?
>>
>>
>> thanks very much!
>>
>> Best!
>>
>> Sam
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
>>
>

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Attachment: trace_credit_sched_both
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