On Sat 02-11-19 15:36:55, zhong jiang wrote: > On 2019/11/2 2:32, Michal Hocko wrote: [...] > > But I would really appreciate to add a comment for the BUG_ON and > > explain why do we care about PageUnevictable so much when there is an > > explicit page_evictable check in the reclaim path. In other words a > > short summary of what Johannes explained in > > http://lkml.kernel.org/r/20191030193307.GA48128@xxxxxxxxxxx. Maybe in a > > separate patch. Care to send one or should I send it? > Hi, Michal > > Actually, I am not very clear about the words Johannes had said. How the race to > tirgger, it will result in an PgeMlocked page can be visible in shrink_page_list. > > Could you elaborate the race in detail further ? I would go with the following comment /* * Page reclaim can see !page_evictable(), but it must not see pages that * have the PageUnevictable lru bit already set. See __pagevec_lru_add_fn() * for more details. */ -- Michal Hocko SUSE Labs
