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Documentation for /proc/sys/vm/* kernel version 2.2.10
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
For general info and legal blurb, please look in README.
==============================================================
This file contains the documentation for the sysctl files in
/proc/sys/vm and is valid for Linux kernel version 2.2.
The files in this directory can be used to tune the operation
of the virtual memory (VM) subsystem of the Linux kernel and
the writeout of dirty data to disk.
Default values and initialization routines for most of these
files can be found in mm/swap.c.
Currently, these files are in /proc/sys/vm:
- overcommit_memory
- page-cluster
- dirty_async_ratio
- dirty_background_ratio
- dirty_expire_centisecs
- dirty_sync_ratio
- dirty_writeback_centisecs
==============================================================
dirty_async_ratio, dirty_background_ratio, dirty_expire_centisecs,
dirty_sync_ratio dirty_writeback_centisecs:
See Documentation/filesystems/proc.txt
==============================================================
overcommit_memory:
This value contains a flag that enables memory overcommitment.
When this flag is 0, the kernel checks before each malloc()
to see if there's enough memory left. If the flag is nonzero,
the system pretends there's always enough memory.
This feature can be very useful because there are a lot of
programs that malloc() huge amounts of memory "just-in-case"
and don't use much of it.
A value of 2 introduces a new "strict overcommit" policy
that attempts to prevent any overcommit of memory.
The default value is 0.
See Documentation/vm/overcommit-accounting and
mm/mmap.c::vm_enough_memory() for more information.
==============================================================
overcommit_ratio:
When overcommit_memory is set to 2, the committed address
space is not permitted to exceed swap plus this percentage
of physical RAM. See above.
==============================================================
page-cluster:
The Linux VM subsystem avoids excessive disk seeks by reading
multiple pages on a page fault. The number of pages it reads
is dependent on the amount of memory in your machine.
The number of pages the kernel reads in at once is equal to
2 ^ page-cluster. Values above 2 ^ 5 don't make much sense
for swap because we only cluster swap data in 32-page groups.
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