Tuning Linux kernel parameters using "sysctl"
This document (3664772) is provided subject to the disclaimer at the end of this document.
SUSE Linux Enterprise Server 9
SUSE Linux Enterprise Desktop 10
When using Oracle products
A package called "orarun" is available for most SUSE Linux products. It should be used when using Oracle product on SUSE Linux products, as it takes care of setting kernel parameters in accordance with Oracle's recommendations.
Listing all available kernel parameters
Using "sysctl -a", the full list of kernel parameters that can be controlled through the sysctl mechanism is displayed, together with their current setting.
Manual setting of kernel parameters
The "sysctl" command can be used to change a kernel setting, e.g.
One important class of tunable kernel parameters is that for Unix System V-style Inter Process Communication (System V IPC). System V IPC encompasses message passing, semaphores and shared memory. Run
Parameters for message passing
kernel.msgmni: number of message queue identifiers
kernel.msgmax: maximum size of a message.
kernel.msgmnb: default maximum size of a message queue (in bytes). On some other Unix systems, this parameter is known as MSGMAP.
MSGTQL: maximum number of message headers system-wide.
MSGPOOL: total size in bytes of the message pool.
MSGSEG: maximum number of message segments per queue.
MSGSSZ: size of a message segment.
Parameters for semaphores
SEMMSL: maximum number of semaphores per id
SEMMNS: maximum number of semaphores, system wide.
SEMOPM: maximum number of operations in one semop call.
SEMMNI: number of semaphore identifiers (or arrays), system wide.
These parameters are set, all together, through kernel.sem which holds the values, separated through whitespace, as follows: SEMMSL SEMMNS SEMOPM SEMMNI.
Not used or not implemented:
SEMAEM: adjust on exit max value.
SEMMNU: number of undo structures system-wide.
SEMUME: maximum number of undo entries per process.
Parameters for shared memory
kernel.shmmni: maximum number of shared segments, system wide
kernel.shmall: maximum shared memory, system wide
kernel.shmmax: maximum shared memory segment size
Not used or not implemented:
SHMSEG: maximum number of shared segments per process
Starting with SLES10 the values for shmall and shmmax are already set to what look like very high values. These values are now set to the maximum for the system by the kernel automatically, so there is no need to change them manually anymore.
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- Document ID:3664772
- Creation Date: 05-Feb-2008
- Modified Date:04-Mar-2021
- SUSE Linux Enterprise Desktop
- SUSE Linux Enterprise Server
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