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Diffstat (limited to 'Documentation/vm/overcommit-accounting')
| -rw-r--r-- | Documentation/vm/overcommit-accounting | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/Documentation/vm/overcommit-accounting b/Documentation/vm/overcommit-accounting index 21c7b1f8f32..cbfaaa67411 100644 --- a/Documentation/vm/overcommit-accounting +++ b/Documentation/vm/overcommit-accounting @@ -4,23 +4,30 @@ The Linux kernel supports the following overcommit handling modes address space are refused. Used for a typical system. It ensures a seriously wild allocation fails while allowing overcommit to reduce swap usage. root is allowed to - allocate slighly more memory in this mode. This is the + allocate slightly more memory in this mode. This is the default. 1 - Always overcommit. Appropriate for some scientific - applications. + applications. Classic example is code using sparse arrays + and just relying on the virtual memory consisting almost + entirely of zero pages. 2 - Don't overcommit. The total address space commit for the system is not permitted to exceed swap + a - configurable percentage (default is 50) of physical RAM. - Depending on the percentage you use, in most situations + configurable amount (default is 50%) of physical RAM. + Depending on the amount you use, in most situations this means a process will not be killed while accessing pages but will receive errors on memory allocation as appropriate. + Useful for applications that want to guarantee their + memory allocations will be available in the future + without having to initialize every page. + The overcommit policy is set via the sysctl `vm.overcommit_memory'. -The overcommit percentage is set via `vm.overcommit_ratio'. +The overcommit amount can be set via `vm.overcommit_ratio' (percentage) +or `vm.overcommit_kbytes' (absolute value). The current overcommit limit and amount committed are viewable in /proc/meminfo as CommitLimit and Committed_AS respectively. |