On Sun 19-10-14 11:30:47, Johannes Weiner wrote: > Better explain re-entrant migration when compaction races with > reclaim, and also mention swapcache readahead pages as possible > uncharged migration sources. > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxx> > --- > mm/memcontrol.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fc1d7ca96b9d..76892eb89d26 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6166,7 +6166,12 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, > if (PageCgroupUsed(pc)) > return; > > - /* Re-entrant migration: old page already uncharged? */ > + /* > + * Swapcache readahead pages can get migrated before being > + * charged, and migration from compaction can happen to an > + * uncharged page when the PFN walker finds a page that > + * reclaim just put back on the LRU but has not released yet. > + */ > pc = lookup_page_cgroup(oldpage); > if (!PageCgroupUsed(pc)) > return; > -- > 2.1.2 > -- Michal Hocko SUSE Labs -- 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>