b44d665368
Currently it accounts the contention using delta between timestamps in lock:contention_begin and lock:contention_end tracepoints. But it means the lock should see the both events during the monitoring period. Actually there are 4 cases that happen with the monitoring: monitoring period / \ | | 1: B------+-----------------------+--------E 2: B----+-------------E | 3: | B-----------+----E 4: | B-------------E | | | t0 t1 where B and E mean contention BEGIN and END, respectively. So it only accounts the case 4 for now. It seems there's no way to handle the case 1. The case 2 might be handled if it saved the timestamp (t0), but it lacks the information from the B notably the flags which shows the lock types. Also it could be a nested lock which it currently ignores. So I think we should ignore the case 2. However we can handle the case 3 if we save the timestamp (t1) at the end of the period. And then it can iterate the map entries in the userspace and update the lock stat accordinly. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Reviewed-by: Ian Rogers <irogers@google.com> Reviwed-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Song Liu <song@kernel.org> Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20240228053335.312776-1-namhyung@kernel.org |
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