Hi Austin, On 05/13/2016 04:14 PM, Austin S. Hemmelgarn wrote: > On 2016-05-13 09:34, Sebastian Frias wrote: >> Hi Austin, >> >> On 05/13/2016 03:11 PM, Austin S. Hemmelgarn wrote: >>> On 2016-05-13 08:39, Sebastian Frias wrote: >>>> >>>> My point is that it seems to be possible to deal with such conditions in a >>>> more controlled way, ie: a way that is less random and less abrupt. >>> There's an option for the OOM-killer to just kill the allocating task >>> instead of using the scoring heuristic. This is about as deterministic as >>> things can get though. >> >> By the way, why does it has to "kill" anything in that case? >> I mean, shouldn't it just tell the allocating task that there's not enough >> memory by letting malloc return NULL? > In theory, that's a great idea. In practice though, it only works if: > 1. The allocating task correctly handles malloc() (or whatever other function > it uses) returning NULL, which a number of programs don't. > 2. The task actually has fallback options for memory limits. Many programs > that do handle getting a NULL pointer from malloc() handle it by exiting > anyway, so there's not as much value in this case. > 3. There isn't a memory leak somewhere on the system. Killing the allocating > task doesn't help much if this is the case of course.
Well, the thing is that the current behaviour, i.e.: overcommiting, does not improves the quality of those programs. I mean, what incentive do they have to properly handle situations 1, 2? Also, if there's a memory leak, the termination of any task, whether it is the allocating task or something random, does not help either, the system will eventually go down, right? > > You have to keep in mind though, that on a properly provisioned system, the > only situations where the OOM killer should be invoked are when there's a > memory leak, or when someone is intentionally trying to DoS the system > through memory exhaustion. Exactly, the DoS attack is another reason why the OOM-killer does not seem a good idea, at least compared to just letting malloc return NULL and let the program fail. >If you're hitting the OOM killer for any other reason than those or a kernel >bug, then you just need more memory or more swap space. > Indeed. Best regards, Sebastian
