I wanted to post a follow up to the list regarding a high
shared_buffers value on OS X 10.4.8.
Thanks to Tom's help we successfully compiled PostgreSQL 8.1.5 using
64-bit on OS X Server 10.4.8 (You can find info. for this on pgports)
shared_buffers can now be set as high as shmmax without getting the
error message "could not create shared memory segment...". Now,
however, when shared_buffers are set greater than 279212 a
segmentation fault occurs on startup of PostgreSQL.
While trying to quantify the performance difference with higher
shared_buffers versus relying more on the kernel cache, the
difference does not appear as significant as I thought. We currently
have shared_buffers set to about 25% of system memory on our box
where we are free to set it within the bounds of shmmax (not OS X, of
course).
Brian Wipf
<brian@clickspace.com>