Section 9.22. Miscellaneous Options

9.22. Miscellaneous Options

These options should always be available and don't depend on any specific subsystem or hardware being present in the system in order to work properly.

Set the number of dentry hash buckets.

dhash_entries= n

This option lets you override the default number of hash buckets for the kernel's dentry cache. Recommended only for kernel experts.

Set the default I/O scheduler elevator.

elevator=[anticipatory|cfq|deadline|noop]

Specify the I/O scheduler. See Chapter 11 for a list of the different I/O schedulers available, and what they do.

Distribute large hashes across NUMA nodes.

hashdist=[0|1]

Large hashes that are allocated during the boot process on the IA-64 platform are, by default, distributed across the different NUMA nodes. This option lets the user turn this option on or off.

Specify IDE driver usage.

combined_mode=[combined|ide|libata]

Control which driver uses the IDE ports in combined mode: the legacy IDE driver, libata, or both. Note that using the ide or libata options may affect your device naming (e.g., by changing hdc to sdb).

Maximum number of loopback devices.

max_loop= n

Specify the maximum number of loopback filesystem devices that can be mounted at the same time. n is an integer from 1 to 256.

Time to wait after panic before rebooting.

panic= n

Specify the amount of time in seconds that the kernel should wait after a panic happens before it reboots. If this is set to 0 (the default value), the kernel will not reboot after panicking; it will simply halt.

Delay between kernel oopses.

pause_on_oops= n

Tell the kernel to halt all CPUs after the first oops for n seconds before continuing. This is useful if oopses keep scrolling off of the screen before you can write them down or take a picture of them.

Control the kernel profiling.

profile= [schedule, ][number]

This option affects how the kernel profiler is calculated. If schedule is specified, the schedule points are affected by the value set in number. If schedule is not specified, number is the step size as a power of two for statistical time-based profiling in the kernel.

The most common use of this option is profile=2.