Performance Tuning for Linux Servers

This section discusses general kernel parameters, including those for the following:

  • Shared memory

  • Processes

  • Signals

  • Profiling/debugging

  • System

Shared Memory

Sysctl Prefix: kernel

/proc Prefix: /proc/sys/kernel/

Parameter

Description

sem

Semaphore values

msgmnb

Maximum message queue in bytes

msgmni

Maximum allowed message queue identifiers

msgmax

Maximum message size in bytes

shmmni

Number of shared segments system-wide

shmall

Shared memory system-wide in pages

shmmax

Shared segment size in bytes

Processes

Sysctl Prefix: kernel

/proc Prefix: /proc/sys/kernel/

Parameter

Description

tHRead_max

Maximum threads allowed in the system

Signals

Sysctl Prefix: kernel

/proc Prefix: /proc/sys/kernel/

Parameter

Description

rtsig-max

Maximum real-time signals

rtsig-nr

Number of currently queued real-time signals

Profiling/Debugging

Sysctl Prefix: kernel

/proc Prefix: /proc/sys/kernel/

Parameter

Description

sysrq

System trace request

printk

Printk values

The printk parameter has four fields: console_loglevel, default_message_ loglevel, minimum_console_level, and default_console_level. Messages with a higher priority than console_loglevel are printed to the console. Messages without an explicit priority are printed with default_message_loglevel priority. The minimum (highest) value to which console_loglevel can be set is determined by the minimum_console_level parameter. The default_console_loglevel is the default value for console_loglevel.

System

Sysctl Prefix: kernel

/proc Prefix: /proc/sys/kernel/

Parameter

Description

domainname

Domain name

hostname

Host name

ostype

Operating system type

osrelease

Operating system release

version

Kernel version

real-root-dev

Real root device partition

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