> Also differs if you turn overcommit off but since so much in linux assumes it your system will soon break if you try it.
I agree, reliance on overcommit has resulted in stability problems in Linux. But IME stability problems aren't induced by disabling overcommit, they're induced by disabling swap. The stability problems occur precisely because by relying on magical heuristics to save the day, we end up with an overall MM architecture that reacts extremely poorly under memory pressure. Whether or not overcommit is enabled, physical memory is a limited resource, and when Linux can't relieve physical memory pressure by dumping pages to disk, bad things happen, especially when under heavy I/O load (e.g. the buffer cache can grab pages faster than the OOM killer can free them).
I agree, reliance on overcommit has resulted in stability problems in Linux. But IME stability problems aren't induced by disabling overcommit, they're induced by disabling swap. The stability problems occur precisely because by relying on magical heuristics to save the day, we end up with an overall MM architecture that reacts extremely poorly under memory pressure. Whether or not overcommit is enabled, physical memory is a limited resource, and when Linux can't relieve physical memory pressure by dumping pages to disk, bad things happen, especially when under heavy I/O load (e.g. the buffer cache can grab pages faster than the OOM killer can free them).