Re: Postgres 8.2 memory weirdness

On Jan 23, 2008 4:31 PM, Greg Smith <gsmith(at)gregsmith(dot)com> wrote:

> Generally if you have a system doing many updates and inserts that slows
> for that long, it's because it hit a checkpoint. I'm not sure what your
> memory-related issues are but it's possible that might be from a backlog
> of sessions using memory that are stuck behind the checkpoint,
> particularly since you mention simple query connections stacking up during
> these periods.
>
> In any case you should prove/disprove this is checkpoint-related behavior
> before you chase down something more esoteric. There's a quick intro to
> this area in the "Monitoring checkpoints" section of
> http://www.westnet.com/~gsmith/content/postgresql/chkp-bgw-83.htm and the
> later sections go into what you can do about it.
>

>

Thanks Greg,

Particulars:

Postg: 8.2.1fc6
Fedora FC6: 2.6.19-1.2911.fc6
Dell 2950, Dual quad core
8 Gigs of Ram
Lefthand Iscsi; 48 drives

Postgres.conf

max_connections = 300
shared_buffers = 75000 <--- Believe these need tuning (based on the
reading last night)
max_prepared_transactions = 0
work_mem = 102400
maintenance_work_mem = 65536
max_fsm_pages = 1087500 <-- modified last night, based on warnings in log
max_fsm_relations = 430
fsync = true
checkpoint_segments = 50
checkpoint_timeout = 300
checkpoint_warning = 3600s <--- set this last night and
already see instances of

"2008-01-24 03:54:39 PST LOG: checkpoints are occurring too
frequently (89 seconds apart)
2008-01-24 03:54:39 PST HINT: Consider increasing the
configuration parameter "checkpoint_segments"."

effective_cache_size = 330000 <-- This appears totally wrong and
something I noticed last night. left over from previous versions of
postgres on different hardware. (thinking to set this to 6-7G)

autovacuum = on
autovacuum_analyze_threshold = 2000

Thanks for the link, I read lots of good information last night and
will start pushing forward with some changes in my test area.

Any insight into what my current settings are telling you is appreciated

-Tory