On Fri, Sep 23, 2022 at 9:07 AM Justin Pryzby <pry...@telsasoft.com> wrote: > On Sun, Aug 28, 2022 at 02:28:02PM -0700, Andres Freund wrote: > > > > > - # Workaround around performance issues due to 32KB block size > > > > > - repartition_script: src/tools/ci/gcp_freebsd_repartition.sh > > > > > create_user_script: | > > > > > pw useradd postgres > > > > > chown -R postgres:postgres . > > > > > > > > What's the story there - at some point that was important for > > > > performance > > > > because of the native block size triggering significant > > > > read-modify-write > > > > cycles with postres' writes. You didn't comment on it in the commit > > > > message. > > > > > > Well, I don't know the history, but it seems to be unneeded now. > > > > It's possible it was mainly needed for testing with aio + dio. But also > > possible that an upgrade improved the situation since.
Yeah, it is very important for direct I/O (patches soon...), because every 8KB random write becomes a read-32KB/wait/write-32KB without it. It's slightly less important for buffered I/O, because the kernel caches hide that, but it still triggers I/O bandwidth amplification, and we definitely saw positive effects earlier on the CI system back on the previous generation. FWIW I am planning to see about getting the FreeBSD installer to create the root file system the way we want, instead of this ugliness. > Maybe freebsd got faster as a result of the TAU CPUs? > [data] Very interesting. Would be good to find the exact instance types + storage types to see if there has been a massive IOPS boost, perhaps via local SSD. The newer times are getting closer to a local developer machine.
