Re: shared memory

OK, John, I think I have an answer for you.  It is not pretty.  You
actually got pretty close.

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.

Sorry I am getting to this so late.  I just finished my book.

--
  Bruce Momjian                        |  http://www.op.net/~candle
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