topic Re: Increasing Shared Memory in Operating System - Linux

Increasing Shared Memory

Jagadesh — Fri, 29 Aug 2003 06:06:42 GMT

How to increase the shared memory in redhat

Can the shared memory be viewed by using free command?
when i say i get the following
[root@redhat root]# free
total used free
Mem: 126152 115360 10792
-/+ buffers/cache: 40848 85304
Swap: 257000 21676 235324

shared buffers cached
0 9076 65436

Kindly help me out in increasing the shared memory

thanks
Jagadesh

Re: Increasing Shared Memory

Stuart Browne — Fri, 29 Aug 2003 06:27:37 GMT

Using either 'top' or 'cat /proc/meminfo' gives you a better overview of what is currently in use.

The 'shared memory' is the amount of memory used by '.so' (shared) libraries. Unless you are using applications written that use shared libraries, the value will usually be little.

You cannot force this value up. It will go up dynamically as applications use it.

Re: Increasing Shared Memory

Mark Grant — Fri, 29 Aug 2003 06:32:45 GMT

Just an addition to stuarts comment, if you really do mean applications using shared memory i.e for inter process communication, ipcs -m will show you what is being used and by who.

Re: Increasing Shared Memory

twang — Fri, 29 Aug 2003 06:44:09 GMT

change without rebuilding kernel or rebooting:
# each > /proc/sys/kernel/shmax
for example,
# echo 22554432 > /proc/sys/kernel/shmmax

note that shared memory setup changes in Linux2.4.

If using oracle, shared memory parameter should be set so that SGA will fit in one segment if possible.