Messages in this thread | | | Subject | Re: overcommit verses MAP_NORESERVE | From | Alan Cox <> | Date | Sun, 07 Aug 2005 12:49:41 +0100 |
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On Sad, 2005-08-06 at 20:52 -0700, Nicholas Miell wrote: > Why does overcommit in mode 2 (OVERCOMMIT_NEVER) explicitly force > MAP_NORESERVE mappings to reserve memory? > > My understanding is that MAP_NORESERVE is a way for apps to state that > they are aware that the memory allocated may not exist and that they > might get a SIGSEGV and that's OK with them.
Because a MAP_NORESERVE space that is filled with pages might cause insufficient memory to be left available for another object that is not MAP_NORESERVE.
You are right it could be improved but that would require someone writing code that forcibly reclaimed MAP_NORESERVE objects when we were close to out of memory. At the moment nobody has done this, but nothing is stopping someone having a go.
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