On Wed, 12 Feb 2020 at 12:36, imai.yoshik...@fujitsu.com <imai.yoshik...@fujitsu.com> wrote:
> It seems performance difference is big in case of read only tests. The reason > is that write time is relatively longer than the > processing time of the logic I added in the patch. That's going to be a pretty difficult performance hit to justify. Can we buffer collected wait events locally and spit the buffer to the stats collector at convenient moments? We can use a limited buffer size with an overflow flag, so we degrade the results rather than falling over or forcing excessive stats reporting at inappropriate times. I suggest that this is also a good opportunity to add some more tracepoints to PostgreSQL. The wait events facilities are not very traceable right now. Exposing some better TRACE_POSTGRESQL_ tracepoints (SDTs) via probes.d would help users collect better information using external tools like perf, bpftrace and systemtap. That way we have a zero-overhead-when-unused option that can also be used to aggregate the information per-query, per-user, etc. (I really need to add a bunch more tracepoints to make this easier...) -- Craig Ringer http://www.2ndQuadrant.com/ 2ndQuadrant - PostgreSQL Solutions for the Enterprise
