linux-kernel - Re: Perf tests for hw events

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Date:	Thu, 22 Jan 2015 13:56:59 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Vince Weaver <vince@...ter.net>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	Kanaka Juvva <kanaka.d.juvva@...el.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: Perf tests for hw events

On Thu, Jan 22, 2015 at 12:40:14PM +0000, Matt Fleming wrote:
> Folks,
> 
> In the process of writing perf support for Intel's Cache QoS Monitoring
> feature [0] I've had to write my own userland tests to drive tools/perf
> and indirectly the kernel internals. I'm now getting requests for these
> tests from various people and it occurs to me that they should probably
> live in the kernel tree.
> 
> The tests I've got do a couple of things like setting up a perf_event
> cgroup and assigning enough tasks to trigger the RMID recycling code in
> the CQM driver, ensuring that we can run multiple events simultaneously
> (that the event scheduling/rotation code works), etc.
> 
> Does anything like this already exist for hw events? I couldn't find
> anything specific to hw events from snooping around in tools/perf/tests. 

that's the only place for this kind of stuff.. and AFAIK we use
just some basic HW events like cycles, or software events

> 
> I propose we add some hw event tests to the kernel tree. These will
> provide,
> 
>  - regression tests
>  - a source of documentation for how to use the events

yes, yes and yes ;-)

> We should only test those hw events that are present on a user's
> machine; there's no sense in emulating things.

agreed.. I remember we were discussing with Arnaldo the strengthening
of the test framework.. so it would detect what tests are runable
under current machine and priviledge

IIRC we already have some CPU detection support:
  int __attribute__ ((weak)) get_cpuid(char *buffer, size_t sz);


jirka
> 
> Thoughts?
> 
> [0] - https://lkml.kernel.org/r/1415999712-5850-1-git-send-email-matt@console-pimps.org
> 
> -- 
> Matt Fleming, Intel Open Source Technology Center
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