On Thu, Feb 02, 2017 at 11:44:22AM +0100, Michal Hocko wrote: > On Tue 31-01-17 14:32:08, Vinayak Menon wrote: > > During global reclaim, the nr_reclaimed passed to vmpressure > > includes the pages reclaimed from slab. But the corresponding > > scanned slab pages is not passed. This can cause total reclaimed > > pages to be greater than scanned, causing an unsigned underflow > > in vmpressure resulting in a critical event being sent to root > > cgroup. So do not consider reclaimed slab pages for vmpressure > > calculation. The reclaimed pages from slab can be excluded because > > the freeing of a page by slab shrinking depends on each slab's > > object population, making the cost model (i.e. scan:free) different > > from that of LRU. > > This might be true but what happens if the slab reclaim contributes > significantly to the overal reclaim? This would be quite rare but not > impossible. Of course, it is better for vmpressure to cover slab but it's not easy without page-based shrinking model, I think. It wold make vmpressure higher easily due to low reclaim efficiency compared to LRU pages. Yeah, vmpressure is not a perfect but no need to add more noises, either. It's regression since 6b4f7799c6a5 so I think this patch should go first and if someone want to cover slab really, he should spend a time to work it well. It's too much that Vinayak shuld make a effort for that. -- 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>
