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Date: Wed, 18 Jan 2017 10:56:58 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Shivappa Vikas <vikas.shivappa@intel.com>,
        Vikas Shivappa <vikas.shivappa@linux.intel.com>, davidcc@google.com,
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        tony.luck@intel.com, fenghua.yu@intel.com, andi.kleen@intel.com,
        h.peter.anvin@intel.com
Subject: Re: [PATCH 00/12] Cqm2: Intel Cache quality monitoring fixes
Message-ID: <20170118095658.GC6485@twins.programming.kicks-ass.net>
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On Wed, Jan 18, 2017 at 09:53:02AM +0100, Thomas Gleixner wrote:
> The whole approach you and David have taken is to whack some desired cgroup
> functionality and whatever into CQM without rethinking the overall
> design. And that's fundamentaly broken because it does not take cache (and
> memory bandwidth) allocation into account.
> 
> I seriously doubt, that the existing CQM/MBM code can be refactored in any
> useful way. As Peter Zijlstra said before: Remove the existing cruft
> completely and start with completely new design from scratch.
> 
> And this new design should start from the allocation angle and then add the
> whole other muck on top so far its possible. Allocation related monitoring
> must be the primary focus, everything else is just tinkering.

Agreed, the little I have seen of these patches is quite horrible. And
there seems to be a definite lack of design; or at the very least an
utter lack of communication of it.

The approach, in so far that I could make sense of it, seems to utterly
rape perf-cgroup. I think Thomas makes a sensible point in trying to
match it to the CAT stuffs.