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    SubjectRe: 2.2/2.4/2.6 VMs: do malloc() ever return NULL?
    Rik van Riel wrote:
    > On Tue, 25 Nov 2003, Ihar 'Philips' Filipau wrote:
    >> 2.6: the same as 2.4 with oom killer (default conf). I have no test
    >> system to check 2.6. w/o oom killer.
    > # echo 2 > /proc/sys/vm/overcommit_memory
    > Then try again.

    What do you know what is not said in docs?
    What '2' means?

    I'll try as soon as I will have again access to 2.6 box.

    this is what 2.6-test10 says:

    > 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.

    Could this special case 'sysctl_overcommit_memory > 1' be added and
    explained? (mmap.c:589)

    I cannot tell what it does - but name 'security_vm_enough_memory()'
    sounds promising ;-)

    As I have said - I will check this later when I will get to those box.

    Ihar 'Philips' Filipau / with best regards from Saarbruecken.
    -- _ _ _
    Because the kernel depends on it existing. "init" |_|*|_|
    literally _is_ special from a kernel standpoint, |_|_|*|
    because its' the "reaper of zombies" (and, may I add, |*|*|*|
    that would be a great name for a rock band).
    -- Linus Torvalds

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