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. 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?). Thanks!
