On Wed, Feb 28, 2024 at 12:16 PM Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote: > > On Wed, Feb 28, 2024 at 12:01:55PM -0800, Namhyung Kim wrote: > > On Wed, Feb 28, 2024 at 4:22 AM Arnaldo Carvalho de Melo > > <acme@xxxxxxxxxx> wrote: > > > > > > On Tue, Feb 27, 2024 at 09:33:35PM -0800, Namhyung Kim wrote: > > > > 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. > > > > > > Perhaps have a separate output listing locks that were found to be with > > > at least tE - t0 time, with perhaps a backtrace at that END time? > > > > Do you mean long contentions in case 3? I'm not sure what do > > you mean by tE, but they started after t0 so cannot be greater > > case 2 > > monitoring period > / \ > | | > 2: B----+-------------E | > | | | > t0 tE t1 > > We get a notification for event E, right? We don´t have one for B, > because it happened before we were monitoring. Ah, ok. But there should be too many events in case 2 and I don't think users want to see them all. And they don't have flags. But maybe we can update the flag when it sees exactly the same callstack later. Thanks, Namhyung
