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Date:      Thu, 28 Jun 2001 16:07:40 -0400
From:      Vivek Khera <khera@kcilink.com>
To:        stable@freebsd.org
Subject:   incorrect comment about SHMALL in LINT
Message-ID:  <15163.36492.238527.989902@onceler.kciLink.com>

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Looking at the LINT file, trying to find some good SHM options to
improve the performance of my PostgreSQL server, I see this:

options         SHMMAXPGS=1025  # max amount of shared memory pages (4k on i386)
options         SHMALL=1025     # max amount of shared memory (bytes)

Now, that second comment smells fishy to me.  I'm suspecting that
should be pages.  So poking around Google, I came across this page:

http://gatekeeper.dec.com/pub/BSD/FreeBSD/FreeBSD-current/src/sys/i386/conf/NOTES

Where it describes the SHM* parameters very clearly and nicely.  This
would be a great addition to 4-STABLE, too, methinks.  Anyhow, this
doc describes the parameters as:

# Maximum size, in bytes, of a single System V shared memory region.
options SHMMAX="(SHMMAXPGS*PAGE_SIZE+1)"
options SHMMAXPGS=1025

# Maximum number of shared memory pages system wide.
options SHMALL=1025 

this latter comment seems to agree with my thinking.  Is this
"documented" incorrectly in the LINT file?

Also, where does one find the defaults, other than "sysctl kern.ipc"
on a running system without the values explicitly specified?

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Vivek Khera, Ph.D.                Khera Communications, Inc.
Internet: khera@kciLink.com       Rockville, MD       +1-240-453-8497
AIM: vivekkhera Y!: vivek_khera   http://www.khera.org/~vivek/

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