On Tue 04-06-19 13:26:51, Minchan Kim wrote: > On Mon, Jun 03, 2019 at 09:16:07AM +0200, Michal Hocko wrote: [...] > > Right. But there is still the page cache reclaim. Is it expected that > > an explicitly cold memory doesn't get reclaimed because we have a > > sufficient amount of page cache (a very common case) and we never age > > anonymous memory because of that? > > If there are lots of used-once pages in file-LRU, I think there is no > need to reclaim anonymous pages because it needs bigger overhead due to > IO. It has been true for a long time in current VM policy. You are making an assumption which is not universally true. If I _know_ that there is a considerable amount of idle anonymous memory then I would really prefer if it goes to the swap rather than make a pressure on caching. Inactive list is not guaranteed to contain only used-once pages, right? Anyway, as already mentioned, we can start with a simpler implementation for now and explicitly note that pagecache biased reclaim is known to be a problem potentially. I am pretty sure somebody will come sooner or later and we can address the problem then with some good numbers to back the additional complexity. -- Michal Hocko SUSE Labs
