Messages in this thread | | | Date | Thu, 2 Feb 2017 09:51:18 -0800 (PST) | From | Shivappa Vikas <> | Subject | RE: [PATCH 00/12] Cqm2: Intel Cache quality monitoring fixes |
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On Wed, 1 Feb 2017, Yu, Fenghua wrote:
>> From: Andi Kleen [mailto:andi@firstfloor.org] >> "Luck, Tony" <tony.luck@intel.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.
This matches the use case where a bunch of real time tasks which have no CLOS id(kernel threads or others in root group) would want to run exclusively on a cpu and are configured so. If any other tasks run there from other class of service we dont want to pullute the cache - hence choose their own CLOSId.
Now in order to measure this RMIds need to match the same policy as CAT.
Thanks, Vikas
> > Thanks. > > -Fenghua >
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