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kernel shared memory calculator
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#!/bin/bash | |
# http://archives.postgresql.org/pgsql-admin/2010-05/msg00285.php | |
# Output lines suitable for sysctl configuration based | |
# on total amount of RAM on the system. The output | |
# will allow up to 50% of physical memory to be allocated | |
# into shared memory. | |
# On Linux, you can use it as follows (as root): | |
# | |
# ./shmsetup >> /etc/sysctl.conf | |
# sysctl -p | |
# Early FreeBSD versions do not support the sysconf interface | |
# used here. The exact version where this works hasn't | |
# been confirmed yet. | |
page_size=`getconf PAGE_SIZE` | |
phys_pages=`getconf _PHYS_PAGES` | |
if [ -z "$page_size" ]; then | |
echo Error: cannot determine page size | |
exit 1 | |
fi | |
if [ -z "$phys_pages" ]; then | |
echo Error: cannot determine number of memory pages | |
exit 2 | |
fi | |
shmall=`expr $phys_pages / 2` | |
shmmax=`expr $shmall \* $page_size` | |
echo \# Maximum shared segment size in bytes | |
echo kernel.shmmax = $shmmax | |
echo \# Maximum number of shared memory segments in pages | |
echo kernel.shmall = $shmall |
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