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d6a2f9035b
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> |
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