On Fri, 19 Aug 2005 20:24:26 -0700, Andrew Morton wrote: > Chuck Ebbert <[EMAIL PROTECTED]> wrote: > > > > +Controls overcommit of system memory: > > It should explain what "overcommit" is.
Here is an improved version. Signed-off-by: Chuck Ebbert <[EMAIL PROTECTED]> Documentation/filesystems/proc.txt | 42 ++++++++++++++++++++++++++++--------- 1 files changed, 32 insertions(+), 10 deletions(-) --- 2.6.13-rc6c.orig/Documentation/filesystems/proc.txt +++ 2.6.13-rc6c/Documentation/filesystems/proc.txt @@ -1240,16 +1240,38 @@ 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. - -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. +Controls overcommit of system memory, possibly allowing processes +to allocate (but not use) more memory than is actually available. + + +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 ---------------------------------- __ Chuck - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
