On Wed, Aug 23, 2017 at 11:38:43PM +0000, Rogozhkin, Dmitry V wrote: > 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? Yes.. x86 used to not allow hotplug of CPU0, but they 'fixed' that :/ And the perf core needs _a_ valid CPU to run things from, which leaves you having to track online/offline things. Now, I suppose its all fairly similar for a lot of uncore PMUs, so maybe you can pull some of this into a library and avoid the endless duplication between all (most?) uncore driveres. > 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. Egads, what a mess :/ Clearly I didn't pay too much attention there. So ideally we'd not hate a state per PMU, and __cpuhp_setup_state_cpuslocked() has a .multi_instance argument that allows reuse of a state. So yes, please use the PERF_X86_UNCORE ones if possible. > 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? Should work with .multi_instance I _think_, I've not had the pleasure of using the new and improved CPU hotplug infrastructure much. > 3. What I should pass as 2nd argument? Will "perf/x86/intel/i915:online" > be ok? Yeah, whatever I think.. something unique. Someone or something will eventually yell if its no good I suppose ;-) _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
