Need help with postgresql/apache/php optimisation

Hello,

I asked one time for more "benchmark" soft to know where is the cpu
average, and read the post about optimising the postgresql.conf (and use
them), but i allways get a load > 1 on fire time (dunno the right name,
"coup de feu" in french (10h00 -> 14h00, 18h00 -> 21h00).

For information, i have a Celeron 1.2Ghz with 256Mb, IDE drive, enough
bandewitch, and about 3000 hit per day. Its postgresql 7.2.lastone,
apache 1.3.lastone, linux (redhat), and the last 2.4 kernel after the
exploit problem. Its not 'my' server, so i cant upgrade anything of it
(RAM is very short i think). Im hosting a web site with apache/php. The
table are not huge, the biggest is aroung 3000rows and only 25-30
tables.

The problem is that on "fire time", the load go to > 1 and stay long
time. But with top (i use top -d 1 to have "real" load average) i can
see that the CPU is more than 50% idling.

For exemple, i have this kind of stat :

0s - load 1.5 - cpu idling 0%
5s - load 1.6 - cpu ilding 50%
6s -> 60s - load around 1.2 - cpu idling around 50%-100%

(Dunno if its very easy to understand).

With different software, i dont see anything wrong (or i dont understand
how to use them), the problem is the memory which make some nice road
around 12Mo Free and 3Mo Free, but the swap dont really grow up (but
linux make a lot of cache).

In fact, i hosted the old site with mysql/apache and i was very happy to
see the load going from 0.90 to 0.40 but the population growing up and
the problem came.

I made the common optimisation with VACUUM ANALYZE and some from the
documentation.

Maybe i dont understand what load average mean, but i dont understand
why with more than 50% cpu idling, the load average dont grow down. So i
thought i lose cpu from somewhere ... but the probleme is what is this
somewhere :).

If someone could help me, i need to put a new feature which will add
more than 2000 hit per day and im afraid about the life of the server
:).

Really thx in advance,

regards,