Fernando Schapachnik <fpscha@ns1.via-net-works.net.ar> writes:
>> enough buffer space to avoid thrashing. You need to increase your
>> kernel's max-shared-memory-block-size (SHMMAX, I think) parameter
>> so that you can run with a more reasonable -B setting. A lot of
>> kernels ship with SHMMAX settings that are ridiculously small for
>> any modern machine.
> What value would you advise for shmmax?
Well, with the default number of buffers (64) Postgres requires about
a megabyte (I think a tad over 1Mb, in 6.5.*). Extra buffers are 8K
plus a little overhead apiece. If you are running with more than a
couple of active backends at a time then you probably want to use
more than the default number of buffers. But I have no advice on
how many is appropriate for what size of installation --- can anyone
else help?
regards, tom lane