On Tue, Aug 26, 2025 at 03:08:06PM +0200, Peter Zijlstra wrote: > On Wed, Aug 13, 2025 at 06:01:08PM +0100, Robin Murphy wrote: > > Sampling is inherently a feature for CPU PMUs, given that the thing > > to be sampled is a CPU context. These days, we have many more > > uncore/system PMUs than CPU PMUs, so it no longer makes much sense to > > assume sampling support by default and force the ever-growing majority > > of drivers to opt out of it (or erroneously fail to). Instead, let's > > introduce a positive opt-in capability that's more obvious and easier to > > maintain. > > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > > index 4d439c24c901..bf2cfbeabba2 100644 > > --- a/include/linux/perf_event.h > > +++ b/include/linux/perf_event.h > > @@ -294,7 +294,7 @@ struct perf_event_pmu_context; > > /** > > * pmu::capabilities flags > > */ > > -#define PERF_PMU_CAP_NO_INTERRUPT 0x0001 > > +#define PERF_PMU_CAP_SAMPLING 0x0001 > > #define PERF_PMU_CAP_NO_NMI 0x0002 > > #define PERF_PMU_CAP_AUX_NO_SG 0x0004 > > #define PERF_PMU_CAP_EXTENDED_REGS 0x0008 > > @@ -305,6 +305,7 @@ struct perf_event_pmu_context; > > #define PERF_PMU_CAP_EXTENDED_HW_TYPE 0x0100 > > #define PERF_PMU_CAP_AUX_PAUSE 0x0200 > > #define PERF_PMU_CAP_AUX_PREFER_LARGE 0x0400 > > +#define PERF_PMU_CAP_NO_INTERRUPT 0x0800 > > So NO_INTERRUPT was supposed to be the negative of your new SAMPLING > (and I agree with your reasoning). > > What I'm confused/curious about is why we retain NO_INTERRUPT? I see from your other reply that you spotted the next patch does that. For the sake of other reviewers or anyone digging through the git history it's probably worth adding a line to this commit message to say: | A subsequent patch will remove PERF_PMU_CAP_NO_INTERRUPT as this | requires some additional cleanup. Mark.
