Messages in this thread | | | Date | Tue, 1 Dec 2009 14:20:08 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH] oom_kill: use rss value instead of vm size for badness |
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On Tue, 1 Dec 2009, KOSAKI Motohiro wrote:
> > The purpose of /proc/pid/oom_adj is not always to polarize the heuristic > > for the task it represents, it allows userspace to define when a task is > > rogue. Working with total_vm as a baseline, it is simple to use the > > interface to tune the heuristic to prefer a certain task over another when > > its memory consumption goes beyond what is expected. With this interface, > > I can easily define when an application should be oom killed because it is > > using far more memory than expected. I can also disable oom killing > > completely for it, if necessary. Unless you have a consistent baseline > > for all tasks, the adjustment wouldn't contextually make any sense. Using > > rss does not allow users to statically define when a task is rogue and is > > dependent on the current state of memory at the time of oom. > > > > I would support removing most of the other heuristics other than the > > baseline and the nodes intersection with mems_allowed to prefer tasks in > > the same cpuset, though, to make it easier to understand and tune. > > I feel you talked about oom_adj doesn't fit your use case. probably you need > /proc/{pid}/oom_priority new knob. oom adjustment doesn't fit you. > you need job severity based oom killing order. severity doesn't depend on any > hueristic. > server administrator should know job severity on his system. >
That's the complete opposite of what I wrote above, we use oom_adj to define when a user application is considered "rogue," meaning that it is using far more memory than expected and so we want it killed. As you mentioned weeks ago, the kernel cannot identify a memory leaker; this is the user interface to allow the oom killer to identify a memory-hogging rogue task that will (probably) consume all system memory eventually. The way oom_adj is implemented, with a bit shift on a baseline of total_vm, it can also polarize the badness heuristic to kill an application based on priority by examining /proc/pid/oom_score, but that wasn't my concern in this case. Using rss as a baseline reduces my ability to tune oom_adj appropriately to identify those rogue tasks because it is highly dynamic depending on the state of the VM at the time of oom.
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