Re: memory leak under heavy load?

> hi
> i think i've encountered a bug in postgresql 8.1.
> yet - i'm not reallty info submitting it to -bugs, as i have no way to
> successfully redo it again.
>
> basically
> i have server, with dual opteron, 4g of memory, 2gb of swap.
> everything working under centos 4.2.
> ...
> what i say is that postmaster user started to "eat" memory.
> it allocated *all* memory (both ram and swap), and then died.
> load on the machine jumped to something around 20.

I noticed a similar occurrence. We have a high-load PostgreSQL database
-- not a ridiculous amount of inserts or updates, but a huge variety of
diverse queries on some 200 tables.

We had noticed load averages of 3-4 on our database for the past couple
days. Then, this morning, Postgres got killed twice by the Linux
out-of-memory process killer. (Also on a dual Opteron, 4GB of memory.)
We were showing 3.5 GB of memory allocated to *something*, but stopping
Postgres completely for a few seconds didn't lower the number. It wasn't
taken by any process, which leads me to believe that it's a kernel bug.
One reboot later, everything is rosy -- load hovers around 1.2, there's
enough free memory to have a 2.5 GB buffer cache, and swap is untouched.

PostgreSQL 7.4 had run on this box flawlessly for six months -- bad RAM
forced us to take it down -- then again for another month until we
upgraded to 8.1 last week. Like the original poster, we're set up for
~500 MB of shared memory; certainly not enough to make the kernel kill
-9 postmaster. Kernel is 2.6.11-gentoo-r6, same as before the upgrade.

Also, this didn't happen in our test environment, which uses a similar
but x86 server. Perhaps this is AMD64 related?

--Will Glynn
Freedom Healthcare