On Tue 06-08-19 03:19:00, Yafang Shao wrote: > In the node reclaim, may_shrinkslab is 0 by default, > hence shrink_slab will never be performed in it. > While shrik_slab should be performed if the relcaimable slab is over > min slab limit. > > Add scan_control::no_pagecache so shrink_node can decide to reclaim page > cache, slab, or both as dictated by min_unmapped_pages and min_slab_pages. > shrink_node will do at least one of the two because otherwise node_reclaim > returns early. > > __node_reclaim can detect when enough slab has been reclaimed because > sc.reclaim_state.reclaimed_slab will tell us how many pages are > reclaimed in shrink slab. > > This issue is very easy to produce, first you continuously cat a random > non-exist file to produce more and more dentry, then you read big file > to produce page cache. And finally you will find that the denty will > never be shrunk in node reclaim (they can only be shrunk in kswapd until > the watermark is reached). > > Regarding vm.zone_reclaim_mode, we always set it to zero to disable node > reclaim. Someone may prefer to enable it if their different workloads work > on different nodes. Considering that this is a long term behavior of a rarely used node reclaim I would rather not touch it unless some _real_ workload suffers from this behavior. Or is there any reason to fix this even though there is no evidence of real workloads suffering from the current behavior? -- Michal Hocko SUSE Labs
