Richard Huxton wrote:

On Sunday 06 Jul 2003 5:54 am, Martin Foster wrote:

The only time that I have ever seen load averages of 30 or more under
OpenBSD is when one of my scripts goes wild.    However, I can say that
I am also seeing these load averages under PostgreSQL 7.3.2 after a
migration to it from MySQL.


However, the system
handled 250 concurrent users without a singular problem, while under
Postgres with new scripts using functions, referential integrity,
transactions and lighter code, the system starts to buckle at even less
then 70 users.


PIII 1Ghz, 1GB
SDRAM, 2 IDE 20GB drives.

I have changed settings to take advantage of the memory.  So the
following settings are of interest:
        shared_buffers = 16384
        wal_buffers = 256
        sort_mem = 16384
        vacuum_mem = 32768

You do know that sort_mem is in kB per sort (not per connection, but per sort being done by a connection). That's 16MB per sort you've allowed in main memory, or for 70 concurrent sorts up to 1.1GB of memory allocated to sorting. You're not going into swap by any chance?

Might want to try halving shared_buffers too and see what happens.

I don't know the *BSDs myself, but do you have the equivalent of iostat/vmstat output you could get for us? Also a snapshot of "top" output? People are going to want to see:
- overall memory usage (free/buffers/cache/swap)
- memory usage per process
- disk activity (blocks in/out)

From that lot, someone will be able to point towards the issue, I'm sure.

Actually, no I did not. Which is probably why it was as high as it is. When looking at the PostgreSQL Hardware Performance Tuning page, it seems to imply that you should calculate based on RAM to give it an appropriate value.

I dropped that value, and will see if that helps. The thing is, the system always indicated plenty of memory available. Even when at a 30 load level the free memory was still roughly 170MB.

Tomorrow will be a good gage to see if the changes will actually help matters. And if they do not, I will include vmstat, iostat, and top as requested.


        Martin Foster
        Creator/Designer Ethereal Realms

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