On Sun, 2020-07-12 at 14:46 -0700, John M. Harris Jr wrote: > That sounds like an excellent idea, but I'm not convinced that killing users' > processes, while there's still tons of memory free available, is actually an > improvement.
I think you should rather think of "MemAvailable" as a measure of how flexible the kernel believes it is in its effort to do memory management. As I said elsewhere already. MemAvailable (i.e. the kernel measure that is read from /proc), does *not* reliably tell you how much memory you can use. There often is no such thing as free memory, it'll be in use for some purpose. And, even worse, the kernel cannot even know. Unless you are already at the point of swapping/thrashing. This is because the kernel does not know know which memory pages the applications are actively using. These measure really are just a guess, rather than a reliably and hard number. If you actually tried to use the memory it says in MemAvailable, you may very well already get bad side effects as the kernel needs to reclaim memory used for other purposes (file caches, mmap'ed executables, heap, …). Depending on the workload, this may already cause the system to start thrashing. I am not trying to claim that EarlyOOM is perfect. These are all just rough heuristics and how well they work will heavily depend on the workload. I am sure you can find scenarios where EarlyOOM will be too aggressive. But, I also think that the people proposing this have done quite a lot of testing to find reasonable values for various scenarios. If they have done their job correctly, then EarlyOOM will *not* prevent you from fully utilizing your system memory in most scenarios. Benjamin
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