perf annotation: Switch lock from a mutex to a sharded_mutex

Remove the "struct mutex lock" variable from annotation that is
allocated per symbol. This removes in the region of 40 bytes per
symbol allocation. Use a sharded mutex where the number of shards is
set to the number of CPUs. Assuming good hashing of the annotation
(done based on the pointer), this means in order to contend there
needs to be more threads than CPUs, which is not currently true in any
perf command. Were contention an issue it is straightforward to
increase the number of shards in the mutex.

On my Debian/glibc based machine, this reduces the size of struct
annotation from 136 bytes to 96 bytes, or nearly 30%.

Signed-off-by: Ian Rogers <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Yuan Can <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

0 files changed, 0 insertions, 0 deletions