alt Hacker NewsNo, this is still misunderstanding.
Overcommit means that the act of memory allocation will not report failure, even when the system is out of memory.
Instead, failure will come at an arbitrary point later, when the program actually attempts to use the aforementioned memory that the system falsely claimed had been allocated.
Allocating all at once on startup doesn't help, because the program can still fail later when it tries to actually access that memory.
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10000truths • today at 1:06 AM
Which is why I said "allocate and pin". POSIX systems have mlock()/mlockall() to prefault allocated memory and prevent it from being paged out.
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To be fair, you can enforce this just by filling all the allocated memory with zero, so it's possible to fail at startup.
Or, even simpler, just turn off over-commit.
But if swap comes into the mix, or just if the OS decides it needs the memory later for something critical, you can still get killed.