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

One observation that we made was right when the statements pile up there
is a large increase in the number of disk reads. The entire issue lasts
approx. 20 secs and then everything recovers. There will be a backlog
of 300+ statements and then all a sudden it seems to get resolved.

We though there might be locking, but noticed that there were not any
queries in wait mode indicating that no statements were blocked by
another statement's lock.

Can anyone suggest what may be causing the pile up/locking like
occurrences?

Brian

-----Original Message-----
From: Richard Huxton [mailto:dev(at)archonet(dot)com]
Sent: Tuesday, October 26, 2004 4:46 AM
To: Brian Maguire
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] what could cause inserts getting queued up and db
locking??

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