On Wed, Apr 25, 2018 at 07:02:42PM +0200, Vlastimil Babka wrote: > 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. Sure, but even just hiding a value isn't that easy now. So we have to touch the vmstat printing code anyway. Thanks!
