tjh.dev
perf vendor events amd: Fix Zen 4 cache latency events
L3PMCx0AC and L3PMCx0AD, used in l3_xi_sampled_latency* events, have a
quirk that requires them to be programmed with SliceId set to 0x3.
Without this, the events do not count at all and affects dependent
metrics such as l3_read_miss_latency.
If ThreadMask is not specified, the amd-uncore driver internally sets
ThreadMask to 0x3, EnAllCores to 0x1 and EnAllSlices to 0x1 but does
not set SliceId. Since SliceId must also be set to 0x3 in this case,
specify all the other fields explicitly.
E.g.
$ sudo perf stat -e l3_xi_sampled_latency.all,l3_xi_sampled_latency_requests.all -a sleep 1
Before:
Performance counter stats for 'system wide':
0 l3_xi_sampled_latency.all
0 l3_xi_sampled_latency_requests.all
1.005155399 seconds time elapsed
After:
Performance counter stats for 'system wide':
921,446 l3_xi_sampled_latency.all
54,210 l3_xi_sampled_latency_requests.all
1.005664472 seconds time elapsed
Fixes: 5b2ca349c313 ("perf vendor events amd: Add Zen 4 uncore events")
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: ananth.narayan@amd.com
Cc: ravi.bangoria@amd.com
Cc: eranian@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240301084431.646221-1-sandipan.das@amd.com
authored by