On Mon, Jul 23, 2018 at 10:53 AM Michael Paquier <mich...@paquier.xyz> wrote: > What's the performance penalty? I am pretty sure that this is > measurable as wait events are stored for a backend for each I/O > operation as well, and you are calling a C routine within an inlined > function which is designed to be light-weight, doing only a four-byte > atomic operation.
Yes, the question is overhead of measuring durations of individual wait events. It has been proposed before, and there been heated debates about that (see threads [1-3]). It doesn't seem to be a conclusion about this feature. The thing to be said for sure: performance penalty heavily depends on OS/hardware/workload. In some cases overhead is negligible, but in other cases it appears to be huge. 1. https://www.postgresql.org/message-id/flat/559D4729.9080704%40postgrespro.ru 2. https://www.postgresql.org/message-id/flat/CA%2BTgmoYd3GTz2_mJfUHF%2BRPe-bCy75ytJeKVv9x-o%2BSonCGApw%40mail.gmail.com 3. https://www.postgresql.org/message-id/flat/CAG95seUAQVj09KzLwU%2Bz1B-GqdMqerzEkPFR3hn0q88XzMq-PA%40mail.gmail.com ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
