Re: CAP and performance problem

[Massimo Canonico <mex@di.unipmn.it>]

I have run other tests, changing the run duration but
it seems that CAP mechanism has some problem.

I always get response time too much longer (3 times instead of 2).

Any idea about how to fix the problem?

Did someone try to make a similar experiment?

Thanks,
  M


On 05/21/2013 04:47 PM, Dario Faggioli wrote:
> On mar, 2013-05-21 at 15:28 +0100, Massimo Canonico wrote:
>> On 05/21/2013 03:06 PM, Dario Faggioli wrote:
>>> Also, when inspecting the vCPU utilization, do you see the VM vCPU busy
>>> up to 100% without cap (or with cap set to 100) and, OTOH, up to 50%
>>> with cap set to 50?
>> I have monitored the CPU usage with xentop during the experiment and
>> I got what you said: my application always use the total amonut of CPU
>> available.
>>
> Ok.
>
>>> Well, looks like a scheduling issue, or, in any case, one where
>>> something is interacting with the scheduling. Can you perhaps boot Dom0
>>> so that it uses only 2 or 3 cores (or arrange for that later, e.g., with
>>> cpupools) and pin the vCPU of the VM on the 4th one?
>> In my experiments, I pin the vCPU of the VM on one core and other cores
>> are pinned to Dom0.
>> [root@csitest ~]# xl vcpu-list
>> Name                                ID  VCPU   CPU State   Time(s) CPU
>> Affinity
>> Domain-0                             0     0    0   ---     383.3  0
>> Domain-0                             0     1    0   -b-     358.1  0
>> Domain-0                             0     2    0   -b-     224.3  0
>> Domain-0                             0     3    0   r--     256.8  0
>> rubis-web                            1     0    2   -b-    9250.9  2
>>
>> (rubis-web is, of course, the VM where my application run)
>>
>> Is this configuration what you meant?
>>
> Sort of. However, since (you said) you have 4 cores, what I was thinking
> was more a situation where you have the 4 Dom0 vCPUs pinned to cores
> 0-2, and the VM vCPU pinned to core 3.
>
> You should be able to achieve that by doing right this:
>
> # xl vcpu-pin 0 all 0-2
> # xl vcpu-pin rubis-web all 3
>
> Does it make sense? Oh, and also, you have 4 _actual_cores_, right? Or
> is there any hyperthreading involved?
>
> Dario
>