I have two more runs of the benchmark in progress so we will have 3 results for each of the test cases to confirm that the small regressions are repeatable.
On Fri, May 5, 2023 at 1:34 PM Andres Freund <andres@anarazel.de> wrote:
One thing that's somewhat odd is that there's very marked changes in l.i0's p99 latency for the four clients cases - but whether 15 or 16 are better differs between the runs.
I do wonder if there's something getting scheduled in some of these runs increasing latency?
Do you mean interference from other processes? Both the big and small servers run Ubuntu 22.04 server (no X) and there shouldn't be many extra things, although Google Cloud adds a few extra things that run in the background.
Both 15 and 16 have one very high result at 70s, 15 then has one low, but 16 has two low results.
Immediately prior to l.i0 the database directory is wiped and then Postgres is initialized and started.
The IPS vs time graphs are more interesting for benchmark steps that run longer. Alas, this can't run too long if the resulting database is to fit in <= 16G. But that is a problem for another day. The IPS vs time graphs are not a flat line, but I am not ready to pursue that as problem unless it shows multi-second write-stalls (fortunately it does not).