Shared memory usage

Hello.

I have a postgres 8.0 and ~400mb database with lots of simple selects
using indexes.
I've installed pgpool on the system. I've set num_init_children to 5 and
here is the top output.
One of postmasters is my demon running some insert/update tasks. I see
that they all use cpu heavily, but do not use the shared memory.
shared_buffers is set to 60000, yet they use a minimal part of that. I'd
like to know why won't they use more? All the indexes and half of the
database should be in the shared memory, is it not? Or am I completely
missing what are the shared_buffers for? If so, then how do I put my
indexes and at least a part of the data into memory?

top - 00:12:35 up 50 days, 13:22,  8 users,  load average: 4.84, 9.71,
13.22
Tasks: 279 total,  10 running, 268 sleeping,   1 stopped,   0 zombie
Cpu(s): 50.0% us, 12.9% sy,  0.0% ni, 33.2% id,  1.8% wa,  0.0% hi,  2.1%
si
Mem:   6102304k total,  4206948k used,  1895356k free,   159436k buffers
Swap:  1959888k total,    12304k used,  1947584k free,  2919816k cached

   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
11492 postgres  16   0  530m  72m  60m S   14  1.2   0:50.91 postmaster
11493 postgres  16   0  531m  72m  60m R   14  1.2   0:48.78 postmaster
11490 postgres  15   0  530m  71m  59m S   13  1.2   0:50.26 postmaster
11491 postgres  15   0  531m  75m  62m S   11  1.3   0:50.67 postmaster
11495 postgres  16   0  530m  71m  59m R   10  1.2   0:50.71 postmaster
10195 postgres  15   0  536m  84m  66m S    6  1.4   1:11.72 postmaster

postgresql.conf:

shared_buffers = 60000
work_mem = 2048
maintenance_work_mem = 256000

The rest are basically default values

Thank you in advance.