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Date: Thu, 2 Feb 2017 01:22:48 +0000
From: "Yu, Fenghua" <fenghua.yu@...el.com>
To: Andi Kleen <andi@...stfloor.org>,
"Luck, Tony" <tony.luck@...el.com>
CC: Thomas Gleixner <tglx@...utronix.de>,
David Carrillo-Cisneros <davidcc@...gle.com>,
Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
"Shivappa, Vikas" <vikas.shivappa@...el.com>,
Stephane Eranian <eranian@...gle.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>,
"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
> From: Andi Kleen [mailto:andi@...stfloor.org]
> "Luck, Tony" <tony.luck@...el.com> writes:
> > 9) Measure per logical CPU (pick active RMID in same precedence for
> task/cpu as CAT picks CLOSID)
> > 10) Put multiple CPUs into a group
>
> I'm not sure this is a real requirement. It's just an optimization, right? If you
> can assign policies to threads, you can implicitly set it per CPU through affinity
> (or the other way around).
> The only benefit would be possibly less context switch overhead, but if all
> the thread (including idle) assigned to a CPU have the same policy it would
> have the same results.
>
> I suspect dropping this would likely simplify the interface significantly.
Assigning a pid P to a CPU and monitoring the P don't count all events happening on the CPU.
Other processes/threads (e.g. kernel threads) than the assigned P can run on the CPU.
Monitoring P assigned to the CPU is not equal to monitoring the CPU in a lot cases.
Thanks.
-Fenghua
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