On 2018-05-01 13:21:21 -0400, Robert Haas wrote: > On Mon, Apr 30, 2018 at 7:08 PM, Andres Freund <and...@anarazel.de> wrote: > >> True, but has anyone ever actually observed a non-zero > >> pg_stat_bgwriter.buffers_backend_fsync in the wild after the > >> compaction queue stuff was added/backpatched? > > > > Yes. > > Care to elaborate?
I unfortunately don't have access to the relevant reports anymore, so it's only by memory. What I do remember is that a few I saw pg_stat_bgwriter.buffers_backend_fsync values that we a pretty sizable fraction of the buffers written by backends. I don't think I ever figured out how problematic that was from a peformance perspective, and how large a fraction of the overall number of fsyncs those were. One was a workload with citus (lots of tables per node), and one was inheritance based partitioning. There were a few others too, where I don't recall anything about the workload. Greetings, Andres Freund
