what could cause inserts getting queued up and db locking??

[Brian Maguire]

Background Info:

I have a table with a approx 2.5 million rows. The table often gets 200-300 inserts per second. We are see that the database (7.4.1 Red Hat Enterprise ED 4 way Xeon) will periodically lock up all of a sudden and force the database to queue up hundreds of queries. The database comes to complete halt until eventually it clears itself out. There is other database activitygoing on but the above activity represents 75% of the frequency of the queries. The table described above has few reads as we try to restrict reads.We have it set so it does one read every 20 seconds collecting all of thenewest data in the last 20 seconds and moves it to a reporting table.

What could cause the database to lock up and queue up all the queries?

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[Richard Huxton]

Brian Maguire wrote:

What could cause the database to lock up and queue up all the
queries?

You'll want to check the lock details (pg_locks: see "Monitoring
Database Activity" in the reference manuals) and also what the system as
a whole is doing (vmstat/iostat).

I seem to recall some configuration of ext3 could cause bursts of
activity with certain write patterns, but don't recall PG being affected
by this.

There have been discussions of context-switching issues with Xeons IIRC
- don't know the details, so check the -performance/hackers archives for
details.

HTH
--
Richard Huxton
Archonet Ltd

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