linux

perf pmu: Use file system cache to optimize sysfs access pmu.c does a lot of redundant /sys accesses while parsing aliases and probing for PMUs. On large systems with a lot of PMUs this can get expensive (>2s): % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 27.25 1.227847 8 160888 16976 openat 26.42 1.190481 7 164224 164077 stat Add a cache to remember if specific file names exist or don't exist, which eliminates most of this overhead. Also optimize some stat() calls to be slightly cheaper access() Resulting in: 0.18 0.004166 2 1851 305 open 0.08 0.001970 2 829 622 access Signed-off-by: Andi Kleen <ak@linux.intel.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: http://lore.kernel.org/lkml/20191121001522.180827-2-andi@firstfloor.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> 2019-11-20 16:15:11 -08:00