FAQ_BSDI

This outlines modifications to BSD/OS for running PostgreSQL:

1)  How to increase resource limits
2)  How to increase the number of shared memory buffers
3)  How to increasing the number of semaphores

Bruce Momjian (pgman@candle.pha.pa.us)  2000-07-7

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1)  To increase the amount of malloc'ed memory and files opened by
PostgreSQL, add this:

          :datasize-cur=600M:\
          :openfiles-cur=256:

to your /etc/login.conf file.

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2a)  By default, only 4MB of shared memory is supported by BSDI. Keep in
mind that shared memory is not pageable.  It is locked in RAM.

To increase the number of buffers supported by the postmaseter, 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.

For those running 4.1 or later, just recompile the kernel and reboot. 
For those running earlier releases, see step 2b.

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2b)  For 4.01 and earlier, 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.

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3)  How to increasing the number of semaphores.

You may need to increase the number of sysv semaphores. By default,
PostgreSQL allocates 32 semaphores, one for each backend connection. 
This is just over half the default system total of 60.

The defaults are in /sys/sys/sem.h:

/* Configuration parameters */
#ifndef SEMMNI
#define SEMMNI  10              /* # of semaphore identifiers */
#endif
#ifndef SEMMNS
#define SEMMNS  60              /* # of semaphores in system */
#endif
#ifndef SEMUME
#define SEMUME  10              /* max # of undo entries per process */
#endif
#ifndef SEMMNU
#define SEMMNU  30              /* # of undo structures in system */
#endif

Set the values you want in your kernel config file, e.g.:

options "SEMMNI=40"
options "SEMMNS=240"
options "SEMUME=40"
options "SEMMNU=120"