On Thu 04-02-16 15:07:47, Johannes Weiner wrote: > Migration accounting in the memory controller used to have to handle > both oldpage and newpage being on the LRU already; fuse's page cache > replacement used to pass a recycled newpage that had been uncharged > but not freed and removed from the LRU, and the memcg migration code > used to uncharge oldpage to "pass on" the existing charge to newpage. > > Nowadays, pages are no longer uncharged when truncated from the page > cache, but rather only at free time, so if a LRU page is recycled in > page cache replacement it'll also still be charged. And we bail out of > the charge transfer altogether in that case. Tell commit_charge() that > we know newpage is not on the LRU, to avoid taking the zone->lru_lock > unnecessarily from the migration path. > > But also, oldpage is no longer uncharged inside migration. We only use > oldpage for its page->mem_cgroup and page size, so we don't care about > its LRU state anymore either. Remove any mention from the kernel doc. > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > Suggested-by: Hugh Dickins <hughd@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > mm/memcontrol.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 3e4199830456..42882c1e7fce 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5489,7 +5489,6 @@ void mem_cgroup_uncharge_list(struct list_head *page_list) > * be uncharged upon free. > * > * Both pages must be locked, @newpage->mapping must be set up. > - * Either or both pages might be on the LRU already. > */ > void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) > { > @@ -5524,7 +5523,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) > page_counter_charge(&memcg->memsw, nr_pages); > css_get_many(&memcg->css, nr_pages); > > - commit_charge(newpage, memcg, true); > + commit_charge(newpage, memcg, false); > > local_irq_disable(); > mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages); > -- > 2.7.0 -- 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>