On Sun 18-09-16 14:18:22, Linus Torvalds wrote: > On Sun, Sep 18, 2016 at 2:00 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote: > > > > Sounds like SLUB. SLAB would use order-0 as long as things fit. I would > > hope for SLUB to fallback to order-0 (or order-1 for 8kB) instead of > > OOM, though. Guess not... > > SLUB it is - and I think that's pretty much all the world these days. > SLAB is largely deprecated. It seems that this is not a general consensus http://lkml.kernel.org/r/20160823153807.GN23577@xxxxxxxxxxxxxx > We should probably start to remove SLAB entirely, and I definitely > hope that no oom people run with it. SLUB is marked default in our > config files, and I think most distros follow that (I know Fedora > does, didn't check others). > > > Well, order-3 is actually PAGE_ALLOC_COSTLY_ORDER, and costly orders > > have to be strictly larger in all the tests. So order-3 is in fact still > > considered "small", and thus it actually results in OOM instead of > > allocation failure. > > Yeah, but I do think that "oom when you have 156MB free and 7GB > reclaimable, and haven't even tried swapping" counts as obviously > wrong. The thing is that swapping doesn't really help. You can easily migrate anonymous memory to create larger blocks even without reclaiming them. So I still believe compaction is giving up too easily. > I'm not saying the code should fail and return NULL either, of course. > > So PAGE_ALLOC_COSTLY_ORDER should *not* mean "oom rather than return > NULL". It really has to mean "try a _lot_ harder". Agreed and Vlastimil's patches go that route. We just do not try sufficiently hard with the compaction. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>