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d484361550
The evlist__for_each_cpu iterator will call sched_setaffitinity when moving between CPUs to avoid IPIs. If only 1 IPI is saved then this may be unprofitable as the delay to get scheduled may be considerable. This may be particularly true if reading an event group in `perf stat` in interval mode. Move the affinity handling completely into the iterator so that a single evlist__use_affinity can determine whether CPU affinities will be used. For `perf record` the change is minimal as the dummy event and the real event will always make the use of affinities the thing to do. In `perf stat`, tool events are ignored and affinities only used if >1 event on the same CPU occur. Determining if affinities are useful is done by evlist__use_affinity which tests per-event whether the event's PMU benefits from affinity use - it is assumed only perf event using PMUs do. Fix a bug where when there are no affinities that the CPU map iterator may reference a CPU not present in the initial evsel. Fix by making the iterator and non-iterator code common. Signed-off-by: Ian Rogers <irogers@google.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andres Freund <andres@anarazel.de> Cc: Dapeng Mi <dapeng1.mi@linux.intel.com> Cc: Dr. David Alan Gilbert <linux@treblig.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Clark <james.clark@linaro.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Falcon <thomas.falcon@intel.com> Cc: Thomas Richter <tmricht@linux.ibm.com> Cc: Yang Li <yang.lee@linux.alibaba.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>