perf/core: Introduce PMU_EV_CAP_READ_ACTIVE_PKG (d6a2f903) · Commits · 戴 / test

Introduce the flag PMU_EV_CAP_READ_ACTIVE_PKG, useful for uncore events, that allows a PMU to signal the generic perf code that an event is readable in the current CPU if the event is active in a CPU in the same package as the current CPU. This is an optimization that avoids a unnecessary IPI for the common case where uncore events are run and read in the same package but in different CPUs. As an example, the IPI removal speeds up perf_read() in my Haswell system as follows: - For event UNC_C_LLC_LOOKUP: From 260 us to 31 us. - For event RAPL's power/energy-cores/: From to 255 us to 27 us. For the optimization to work, all events in the group must have it (similarly to PERF_EV_CAP_SOFTWARE). Signed-off-by:

David Carrillo-Cisneros <davidcc@google.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Carrillo-Cisneros <davidcc@google.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kan Liang <kan.liang@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul Turner <pjt@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vegard Nossum <vegard.nossum@gmail.com> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: http://lkml.kernel.org/r/1471467307-61171-4-git-send-email-davidcc@google.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

include/linux/perf_event.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -514,8 +514,11 @@ typedef void (perf_overflow_handler_t)(struct perf_event ,
		* Event capabilities. For event_caps and groups caps.
		*
		* PERF_EV_CAP_SOFTWARE: Is a software event.
		* PERF_EV_CAP_READ_ACTIVE_PKG: A CPU event (or cgroup event) that can be read
		* from any CPU in the package where it is active.
		*/
		#define PERF_EV_CAP_SOFTWARE BIT(0)
		#define PERF_EV_CAP_READ_ACTIVE_PKG BIT(1)

		#define SWEVENT_HLIST_BITS 8
		#define SWEVENT_HLIST_SIZE (1 << SWEVENT_HLIST_BITS)

kernel/events/core.c

+23 −2

Original line number	Diff line number	Diff line
		@@ -3424,6 +3424,22 @@ struct perf_read_data {
		int ret;
		};

		static int find_cpu_to_read(struct perf_event *event, int local_cpu)
		{
		int event_cpu = event->oncpu;
		u16 local_pkg, event_pkg;

		if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {
		event_pkg = topology_physical_package_id(event_cpu);
		local_pkg = topology_physical_package_id(local_cpu);

		if (event_pkg == local_pkg)
		return local_cpu;
		}

		return event_cpu;
		}

		/*
		* Cross CPU call to read the hardware event
		*/
		@@ -3545,7 +3561,7 @@ u64 perf_event_read_local(struct perf_event *event)

		static int perf_event_read(struct perf_event *event, bool group)
		{
		int ret = 0;
		int ret = 0, cpu_to_read, local_cpu;

		/*
		* If event is enabled and currently active on a CPU, update the
		@@ -3557,7 +3573,12 @@ static int perf_event_read(struct perf_event *event, bool group)
		.group = group,
		.ret = 0,
		};
		ret = smp_call_function_single(event->oncpu, __perf_event_read, &data, 1);

		local_cpu = get_cpu();
		cpu_to_read = find_cpu_to_read(event, local_cpu);
		put_cpu();

		ret = smp_call_function_single(cpu_to_read, __perf_event_read, &data, 1);
		/* The event must have been read from an online CPU: */
		WARN_ON_ONCE(ret);
		ret = ret ? : data.ret;

Admin message