Re: [PATCH 16/19] perf: Introduce positive capability for sampling
Peter Zijlstra <[email protected]>
| Newsgroups | gmane.comp.freedesktop.xorg.drivers.intel,gmane.linux.kernel.perf.user,gmane.linux.kernel,gmane.linux.ports.alpha,gmane.linux.kernel.arc,gmane.linux.ports.arm.kernel,gmane.linux.ports.mips,gmane.linux.ports.ppc64.devel,gmane.linux.ports.sh.devel,gmane.linux.ports.sparc,gmane.linux.power-management.general,gmane.linux.ports.arm.rockchip,gmane.comp.freedesktop.amd-gfx,gmane.comp.video.dri.devel,gmane.linux.ports.arm.msm,gmane.linux.ports.riscv |
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| Message-ID | <[email protected]> |
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?