Re: [PATCH 16/19] perf: Introduce positive capability for sampling
From: Peter Zijlstra <peterz@infradead.org>
Date: 2025-08-26 13:08:13
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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.
quoted hunk ↗ jump to hunk
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?