[Intel-gfx] [RFC v2 2/3] drm/i915/pmu: serve global events and support perf stat

Wed Aug 23 23:38:43 UTC 2017

On Wed, 2017-08-23 at 08:26 -0700, Dmitry Rogozhkin wrote:
> +static cpumask_t i915_pmu_cpumask = CPU_MASK_CPU0;

Peter, this hardcoding of cpumask to use CPU0 works, but should I
implement something smarter or this will be sufficient? I see that
cstate.c you have pointed me to tries to track CPUs going online/offline
and migrates PMU context to another CPU if selected one went offline.
Should I follow this way?

If I should track CPUs going online/offline, then I have questions:
1. How I should register tracking callbacks? I see that cstate.c
registers CPUHP_AP_PERF_X86_CSTATE_STARTING and
CPUHP_AP_PERF_X86_CSTATE_ONLINE, uncore.c registers
CPUHP_AP_PERF_X86_UNCORE_ONLINE. What I should use? I incline to UNCORE.
2. If I will register for, say UNCORE, then how double registrations
will be handled if both uncore.c and i915.c will register callbacks? Any
conflict here?
3. What I should pass as 2nd argument? Will "perf/x86/intel/i915:online"
be ok?