Re: Perf tests for hw events

[Matt Fleming <matt@codeblueprint.co.uk>]

On Thu, 22 Jan, at 01:56:59PM, Jiri Olsa wrote:
> 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
 
OK cool. I just wanted confirmation that tools/perf/tests was the best
place for these tests.

> > 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);

Aha, excellent. I hadn't noticed this. It should be possible to build
something on top of this.

-- 
Matt Fleming, Intel Open Source Technology Center