Hi, On 2019-01-22 14:53:11 -0600, Kevin Grittner wrote: > On Tue, Jan 22, 2019 at 2:38 PM Andres Freund <and...@anarazel.de> wrote: > > > close() doesn't trigger an fsync() in general > > What sort of a performance hit was observed when testing the addition > of fsync or fdatasync before any PostgreSQL close() of a writable > file, or have we not yet checked that?
I briefly played with it, and it was so atrocious (as in, less than something like 0.2x the throughput) that I didn't continue far down that path. Two ways I IIRC (and it's really just memory) I tried were: a) Short lived connections that do a bunch of writes to files each. That turns each disconnect into an fsync of most files. b) Workload with > max_files_per_process files (IIRC I just used a bunch of larger tables with a few indexes each) in a read/write workload that's a bit larger than shared buffers. That lead to most file closes being integrity writes, with obvious downsides. Greetings, Andres Freund
