This outlines how to increase the number of shared memory buffers

supported by BSD/OS. By default, only 4MB of shared memory is supported

by BSDI.

Bruce Momjian (pgman@candle.pha.pa.us)

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First, increase SHMMAXPGS by 1024 for every additional 4MB of shared

memory:

/sys/sys/shm.h:69:#define SHMMAXPGS 1024 /* max hardware pages...

The default setting of 1024 is for a maximum of 4MB of shared memory.

Second, use bpatch to find the sysptsize value for the current kernel.

This is computed dynamically at bootup.

$ bpatch -r sysptsize

0x9 = 9

Next, change SYSPTSIZE to a hard-coded value. Use the bpatch value,

plus add 1 for every additional 4MB of shared memory you desire.

/sys/i386/i386/i386_param.c:28:#define SYSPTSIZE 0 /* dynamically...

sysptsize can not be changed by sysctl on the fly.

This should clearly be easier to do on BSDI. I will add a BSDI FAQ for

PostgreSQL to cover this. One downside is that shared memory is not

pageable. It is locked in RAM.