On 2014/04/28 07:50 PM, Tom Lane wrote:
Michael van Rooyen <michael@xxxxxxxxxx> writes:
I'm trying to get to the bottom of a performance issue on a server
running PostgreSQL 9.3.1 on Centos 5.
Hm ... it seems pretty suspicious that all of these examples take just
about exactly 1 second longer than you might expect. I'm wondering
if there is something sitting on an exclusive table lock somewhere,
and releasing it after 1 second.
I do have log_min_duration_statement = 1000, which may cause this.
In particular, this looks quite a bit like the old behavior of autovacuum
when it was trying to truncate empty pages off the end of a relation ---
it would hold off other accesses to the table until deadlock_timeout
elapsed, whereupon it'd get kicked off the exclusive lock (and have to
retry the truncation next time). Are you *sure* this server is running
9.3.1, and not something pre-9.3?
Definitely 9.3.1. The strange thing is I have other servers with
similar configurations and load and with the same database, where
performance is great, so it's hard for me to know what's different
here. Maybe I'm expecting too much from these SATA drives, or it's time
to add lots of RAM...
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