On Thu, Feb 04, 2016 at 03:07:47PM -0500, 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: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Nit: diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ae8b81c55685..120118f3ce0a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5483,6 +5483,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) unsigned int nr_pages; bool compound; + VM_BUG_ON_PAGE(PageLRU(newpage), newpage); VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); VM_BUG_ON_PAGE(PageAnon(oldpage) != PageAnon(newpage), newpage); -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
