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Date: Thu, 2 Feb 2017 19:33:15 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: David Carrillo-Cisneros <davidcc@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>
CC: 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>,
"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
>> Nice to have:
>> 1) Readout using "perf(1)" [subset of modes that make sense ... tying monitoring
>> to resctrl file system will make most command line usage of perf(1) close to impossible.
>
>
> We discussed this offline and I still disagree that it is close to
> impossible to use perf and perf_event_open. In fact, I think it's very
> simple :
Maybe s/most/many/ ?
The issue here is that we are going to define which tasks and cpus are being
monitored *outside* of the perf command. So usage like:
# perf stat -I 1000 -e intel_cqm/llc_occupancy {command}
are completely out of scope ... we aren't planning to change the perf(1)
command to know about creating a CQM monitor group, assigning the
PID of {command} to it, and then report on llc_occupancy.
So perf(1) usage is only going to support modes where it attaches to some
monitor group that was previously established. The "-C 2" option to monitor
CPU 2 is certainly plausible ... assuming you set up a monitor group to track
what is happening on CPU 2 ... I just don't know how perf(1) would know the
name of that group.
Vikas is pushing for "-R rdtgroup" ... though our offline discussions included
overloading "-g" and have perf(1) pick appropriately from cgroups or rdtgroups
depending on event type.
-Tony
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