linux/tools/perf/util/fncache.h
Andi Kleen d96645821e 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>
2019-11-28 08:08:38 -03:00

8 lines
126 B
C

#ifndef _FCACHE_H
#define _FCACHE_H 1
unsigned shash(const unsigned char *s);
bool file_available(const char *name);
#endif