Bernd Helmle wrote:
I've tried to benchmark this now on my (fairly slow compared to server
hardware) MacBook and see some negative trend for those memory probes
in pgbench. Running dozens of rounds with pgbench (scale 150, 10
clients / 1000 transactions)
That makes for a 5.5 minute test, which is unfortunately close to the
default checkpoint period. You're going to want a pgbench configuration
that's doing thousands of operations per second to measure this overhead
I think, and let it run a bit longer. The difference you're seeing
could easily be just that that the "with probes" result had more
checkpoints happen during testing than the other one--if it got even a
single checkpoint more, that could be enough to throw results off using
the default test and such low TPS results.
Try this instead, which will give you a test where checkpoints have a
minimal impact, but lots of memory will be thrown around:
pgbench -i -s 10 <db>
pgbench -S -c 10 -T 600 <db>
That will do just SELECT statements against a much smaller database
(about 160MB) and will run for 10 minutes each time.
--
Greg Smith 2ndQuadrant Baltimore, MD
PostgreSQL Training, Services and Support
g...@2ndquadrant.com www.2ndQuadrant.com
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