Re: [GENERAL] Tuning PostgreSQL to use more RAM...

[Tom Lane]

"Steve Wolfe" <[EMAIL PROTECTED]> writes:
>While I don't mind disk cache, I feel that we could get better
> performance by letting postgres use another hundred megs or so, especially
> since our entire /usr/local/pgsql/base directory has only 134 megs of data.
> We're currently starting the postmaster with "-B 2048".

You might try increasing the default -S setting as well.

I am not convinced that increasing -B to huge values will be a net win.
At some point you will start losing performance due to the sequential
scans of the buffer cache that are done at transaction commit (and other
places IIRC).  I haven't done any benchmarking of different settings,
however, so I have no idea what the optimal level might be.

regards, tom lane

[GENERAL] Tuning PostgreSQL to use more RAM...

[Steve Wolfe]

> Actually, more RAM would permit you to increase both the -B parameters as
> well as the -S one ... which are both noted for providing performance
> increases ... -B more on repeative queries and -S on anything involving
> ORDER BY or GROUP BY ...

  For a while now, I've been meaning to investigate how to get PostgreSQL to
take advantage of the RAM in our machine.  It has 512 megs, and most of the
time, about 275-400 megs of it simply go to disk cache & buffer, as nothing
else wants it.  Occasionally, we'll only have 250-300 megs of disk cache.
: )

   While I don't mind disk cache, I feel that we could get better
performance by letting postgres use another hundred megs or so, especially
since our entire /usr/local/pgsql/base directory has only 134 megs of data.
We're currently starting the postmaster with "-B 2048".  The machine has 4
Xeon processors, and 5 drives in the RAID array, so we do have a small bit
of CPU power and disk throughput.  Any suggestions or pointers are welcome.

steve