Re: Adding RAM: seeking advice & warnings of hidden "gotchas"

On Dec 17, 2003, at 11:57 AM, Nick Fankhauser wrote:

> Hi-
>
> After having done my best to squeeze better performance out of our
> application by tuning within our existing resources, I'm falling back
> on
> adding memory as a short-term solution while we get creative for a
> long-term
> fix. I'm curious about what experiences others have had with the
> process of
> adding big chunks of RAM. In particular, if I'm trying to encourage
> the OS
> to cache more of my index information in RAM, what sort of
> configuration
> should I do at both the PostgreSQL and OS level?

You need bigmem compiled in the kernel, which you should already have
at the 1 gig level iirc.
You should bump up your effective cache size, probably to around 1.75
gig.

I wouldn't bump up the shared buffers beyond where you have them now.
If you're swapping out sorts to disk, you may gain boosting sortmem
some since you have the additional memory to use.

> The server is a dual processor Athlon 1.2GHz box with hardware SCSI
> RAID. It
> currently has 1 GB RAM, and we're planning to add one GB more for a
> total of
> 2GB. The OS is Debian Linux Kernel 2.4.x, and we're on PostgreSQL
> v7.3.2

I've got a machine running Debian Stable w/2.4.x, 1.3 ghz p3, 1.5 gig
ram, pg 7.2.4 and it's rock solid.

eric