Linux kernel memory overcommiting

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Linux kernel memory overcommiting

Postby lik » Mon Sep 14, 2009 10:54 pm

1 The Linux kernel supports the following overcommit handling modes
3 0 - Heuristic overcommit handling. Obvious overcommits of
4 address space are refused. Used for a typical system. It
5 ensures a seriously wild allocation fails while allowing
6 overcommit to reduce swap usage. root is allowed to
7 allocate slighly more memory in this mode. This is the
8 default.
10 1 - Always overcommit. Appropriate for some scientific
11 applications.
13 2 - Don't overcommit. The total address space commit
14 for the system is not permitted to exceed swap + a
15 configurable percentage (default is 50) of physical RAM.
16 Depending on the percentage you use, in most situations
17 this means a process will not be killed while accessing
18 pages but will receive errors on memory allocation as
19 appropriate.
21 The overcommit policy is set via the sysctl `vm.overcommit_memory'.
23 The overcommit percentage is set via `vm.overcommit_ratio'.
25 The current overcommit limit and amount committed are viewable in
26 /proc/meminfo as CommitLimit and Committed_AS respectively.
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