Kevin Grittner wrote:
I wonder if it might also pay to make the background writer even more
aggressive than we have, so that SELECT-only queries don't spend so
much time writing pages.
You can easily quantify if the BGW is aggressive enough. Buffers leave
the cache three ways, and they each show up as separate counts in
pg_stat_bgwriter: buffers_checkpoint, buffers_clean (the BGW), and
buffers_backend (the queries). Cranking it up further tends to shift
writes out of buffers_backend, which are the ones you want to avoid,
toward buffers_clean instead. If buffers_backend is already low on a
percentage basis compared to the other two, there's little benefit in
trying to make the BGW do more.
--
Greg Smith 2ndQuadrant Baltimore, MD
PostgreSQL Training, Services and Support
greg@xxxxxxxxxxxxxxx www.2ndQuadrant.com
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