On 04/25/2018 06:48 PM, Roman Gushchin wrote: > On Wed, Apr 25, 2018 at 05:47:26PM +0200, Vlastimil Babka wrote: >> On 04/25/2018 02:52 PM, Roman Gushchin wrote: >>> On Wed, Apr 25, 2018 at 09:19:29AM +0530, Vijayanand Jitta wrote: >>>>>>>> Idk, I don't like the idea of adding a counter outside of the vm counters >>>>>>>> infrastructure, and I definitely wouldn't touch the exposed >>>>>>>> nr_slab_reclaimable and nr_slab_unreclaimable fields. >>>>>>> >>>>>>> We would be just making the reported values more precise wrt reality. >>>>>> >>>>>> It depends on if we believe that only slab memory can be reclaimable >>>>>> or not. If yes, this is true, otherwise not. >>>>>> >>>>>> My guess is that some drivers (e.g. networking) might have buffers, >>>>>> which are reclaimable under mempressure, and are allocated using >>>>>> the page allocator. But I have to look closer... >>>>>> >>>>> >>>>> One such case I have encountered is that of the ION page pool. The page pool >>>>> registers a shrinker. When not in any memory pressure page pool can go high >>>>> and thus cause an mmap to fail when OVERCOMMIT_GUESS is set. I can send >>>>> a patch to account ION page pool pages in NR_INDIRECTLY_RECLAIMABLE_BYTES. >> >> FYI, we have discussed this at LSF/MM and agreed to try the kmalloc >> reclaimable caches idea. The existing counter could then remain for page >> allocator users such as ION. It's a bit weird to have it in bytes and >> not pages then, IMHO. What if we hid it from /proc/vmstat now so it >> doesn't become ABI, and later convert it to page granularity and expose >> it under a name such as "nr_other_reclaimable" ? > > I've nothing against hiding it from /proc/vmstat, as long as we keep > the counter in place and the main issue resolved. Sure. > Maybe it's better to add nr_reclaimable = nr_slab_reclaimable + nr_other_reclaimable, > which will have a simpler meaning that nr_other_reclaimable (what is other?). "other" can be changed, sure. nr_reclaimable is possible if we change slab to adjust that counter as well - vmstat code doesn't support arbitrary calculations when printing. > Thanks! >
