On Fri, Nov 02, 2018 at 06:48:23PM +0100, Michal Hocko wrote: > On Fri 02-11-18 17:25:58, Roman Gushchin wrote: > > On Fri, Nov 02, 2018 at 05:51:47PM +0100, Michal Hocko wrote: > > > On Fri 02-11-18 16:22:41, Roman Gushchin wrote: > [...] > > > > 2) We do forget to scan the last page in the LRU list. So if we ended up with > > > > 1-page long LRU, it can stay there basically forever. > > > > > > Why > > > /* > > > * If the cgroup's already been deleted, make sure to > > > * scrape out the remaining cache. > > > */ > > > if (!scan && !mem_cgroup_online(memcg)) > > > scan = min(size, SWAP_CLUSTER_MAX); > > > > > > in get_scan_count doesn't work for that case? > > > > No, it doesn't. Let's look at the whole picture: > > > > size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); > > scan = size >> sc->priority; > > /* > > * If the cgroup's already been deleted, make sure to > > * scrape out the remaining cache. > > */ > > if (!scan && !mem_cgroup_online(memcg)) > > scan = min(size, SWAP_CLUSTER_MAX); > > > > If size == 1, scan == 0 => scan = min(1, 32) == 1. > > And after proportional adjustment we'll have 0. > > My friday brain hurst when looking at this but if it doesn't work as > advertized then it should be fixed. I do not see any of your patches to > touch this logic so how come it would work after them applied? This part works as expected. But the following scan = div64_u64(scan * fraction[file], denominator); reliable turns 1 page to scan to 0 pages to scan. And this is the issue which my patches do address. Thanks!
