On Nov 10, 2006, at 6:35 PM, Nguyen Tam Chinh wrote:
For the pg configuration, I use this on a 4Gb box:
max_connections = 100
shared_buffers = 70000 # min 16 or
max_connections*2, 8KB each
work_mem = 262144 # min 64, size in KB
Thank you very much. And how did you set the semaphore's
parameters? Do you have any trick or experience? I just think it's
just weird to inceremently increase ipc.shm* and ipc.sem* to get
the right values. The documentation of PostGreSQL gives us some
examples but without explanation how they found those values.
The SEM parameters are the bare minimum. Pg uses a small number of
semaphores, so unless you have a bazillion connections allowed, just
use these settings:
kern.ipc.semmsl=512
kern.ipc.semmap=256
kern.ipc.semmni=32
kern.ipc.semmns=512
Now, for the SHM usage, it is just arithmetic. You now how many
buffers you're asking for, you know how big they are, and you just
need to add some for overhead and you've got your number. If you
want Pg to compute it for you, just read the error log when you fire
up Pg with a small shm setting in the OS.
