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Diffstat (limited to 'Documentation/filesystems/proc.txt')
| -rw-r--r-- | Documentation/filesystems/proc.txt | 41 |
1 files changed, 32 insertions, 9 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 6c98f2bd421..d4773565ea2 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -133,6 +133,7 @@ Table 1-1: Process specific entries in /proc statm Process memory status information status Process status in human readable form wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan + smaps Extension based on maps, presenting the rss size for each mapped file .............................................................................. For example, to get the status information of a process, all you have to do is @@ -1240,16 +1241,38 @@ swap-intensive. overcommit_memory ----------------- -This file contains one value. The following algorithm is used to decide if -there's enough memory: if the value of overcommit_memory is positive, then -there's always enough memory. This is a useful feature, since programs often -malloc() huge amounts of memory 'just in case', while they only use a small -part of it. Leaving this value at 0 will lead to the failure of such a huge -malloc(), when in fact the system has enough memory for the program to run. +Controls overcommit of system memory, possibly allowing processes +to allocate (but not use) more memory than is actually available. -On the other hand, enabling this feature can cause you to run out of memory -and thrash the system to death, so large and/or important servers will want to -set this value to 0. + +0 - Heuristic overcommit handling. Obvious overcommits of + 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 + default. + +1 - Always overcommit. Appropriate for some scientific + applications. + +2 - Don't overcommit. The total address space commit + for the system is not permitted to exceed swap plus a + configurable percentage (default is 50) of physical RAM. + Depending on the percentage you use, in most situations + this means a process will not be killed while attempting + to use already-allocated memory but will receive errors + on memory allocation as appropriate. + +overcommit_ratio +---------------- + +Percentage of physical memory size to include in overcommit calculations +(see above.) + +Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100) + + swapspace = total size of all swap areas + physmem = size of physical memory in system nr_hugepages and hugetlb_shm_group ---------------------------------- |