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

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Message-ID: <alpine.DEB.2.20.1702171300400.3536@nanos>
Date:   Fri, 17 Feb 2017 14:41:54 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Stephane Eranian <eranian@...gle.com>
cc:     "Luck, Tony" <tony.luck@...el.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        "Shivappa, Vikas" <vikas.shivappa@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>,
        "Anvin, H Peter" <h.peter.anvin@...el.com>
Subject: Re: [PATCH 00/12] Cqm2: Intel Cache quality monitoring fixes

On Tue, 7 Feb 2017, Stephane Eranian wrote:
> 
> I think the design must ensure that the following usage models can be monitored:
>    - the allocations in your CAT partitions
>    - the allocations from a task (inclusive of children tasks)
>    - the allocations from a group of tasks (inclusive of children tasks)
>    - the allocations from a CPU
>    - the allocations from a group of CPUs

What's missing here is:

     - the allocations of a subset of users (tasks/groups/cpu(s)) of a
       particular CAT partition

Looking at your requirement list, all requirements, except the first point,
have no relationship to CAT (at least not from your write up). Now the
obvious questions are:

 - Does it make sense to ignore CAT relations in these sets?

 - Does it make sense to monitor a task / group of tasks, where the tasks
   belong to different CAT partitions?

 - Does it make sense to monitor a CPU / group of CPUs as a whole
   independent of which CAT partitions have been utilized during the
   monitoring period?

I don't think it makes any sense, unless the resulting information is split
up into CAT partitions.

I'm happy to be educated on the value of making this CAT unaware, but so
far I only came up with results, which need a crystal ball to analyze them.

Thanks,

	tglx