Re: [PATCH 00/12] Cqm2: Intel Cache quality monitoring fixes

[David Carrillo-Cisneros]

On Fri, Jan 20, 2017 at 12:30 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> On Thu, 19 Jan 2017, David Carrillo-Cisneros wrote:
>> On Thu, Jan 19, 2017 at 9:41 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>> > Above you are talking about the same CLOSID and different RMIDS and not
>> > about changing both.
>>
>> The scenario I talked about implies changing CLOSID without affecting
>> monitoring.
>> It happens when the allocation needs for a thread/cgroup/CPU change
>> dynamically. Forcing to change the RMID together with the CLOSID would
>> give wrong monitoring values unless the old RMID is kept around until
>> becomes free, which is ugly and would waste a RMID.
>
> When the allocation needs for a resource control group change, then we
> simply update the allocation constraints of that group without chaning the
> CLOSID. So everything just stays the same.
>
> If you move entities to a different group then of course the CLOSID
> changes and then it's a different story how to deal with monitoring.
>
>> > To gather any useful information for both CPU1 and T1 you need TWO
>> > RMIDs. Everything else is voodoo and crystal ball analysis and we are not
>> > going to support that.
>> >
>>
>> Correct. Yet, having two RMIDs to monitor the same task/cgroup/CPU
>> just because the CLOSID changed is wasteful.
>
> Again, the CLOSID only changes if you move entities to a different resource
> control group and in that case the RMID change is the least of your worries.
>
>> Correct. But there may not be a fixed CLOSID association if loads
>> exhibit dynamic behavior and/or system load changes dynamically.
>
> So, you really want to move entities around between resource control groups
> dynamically? I'm not seing why you would want to do that, but I'm all ear
> to get educated on that.

No, I don't want to move entities across resource control groups. I
was confused by the idea of CLOSIDs being married to control groups,
but now is clear even to me that that was never the intention.

Thanks,
David

>
> Thanks,
>
>         tglx