KAMEZAWA Hiroyuki wrote: > While using memory control cgroup, page-migration under it works as following. > == > 1. uncharge all refs at try to unmap. > 2. charge regs again remove_migration_ptes() > == > This is simple but has following problems. > == > The page is uncharged and chaged back again if *mapped*. > - This means that cgroup before migraion can be different from one after > migraion > - If page is not mapped but charged as page cache, charge is just ignored > (because not mapped, it will not be uncharged before migration) > This is memory leak. > == > This patch tries to keep memory cgroup at page migration by increasing > one refcnt during it. 3 functions are added. > > mem_cgroup_prepare_migration() --- increase refcnt of page->page_cgroup > mem_cgroup_end_migration() --- decrease refcnt of page->page_cgroup > mem_cgroup_page_migration() --- copy page->page_cgroup from old page to > new page. > > During migration > - old page is under PG_locked. > - new page is under PG_locked, too. > - both old page and new page are not on LRU. > > These 3 facts guarantees page_cgroup() migration has no race, I think. > > Tested and worked well in x86_64/fake-NUMA box. > > Changelog v1 -> v2: > - reflected comments. > - divided a patche to !PageLRU patch and migration patch. > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > include/linux/memcontrol.h | 19 +++++++++++++++++++ > mm/memcontrol.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > mm/migrate.c | 14 +++++++++++--- > 3 files changed, 73 insertions(+), 3 deletions(-) > > Index: devel-2.6.23-rc8-mm2/mm/migrate.c > =================================================================== > --- devel-2.6.23-rc8-mm2.orig/mm/migrate.c > +++ devel-2.6.23-rc8-mm2/mm/migrate.c > @@ -598,9 +598,10 @@ static int move_to_new_page(struct page > else > rc = fallback_migrate_page(mapping, newpage, page); > > - if (!rc) > + if (!rc) { > + mem_cgroup_page_migration(page, newpage); > remove_migration_ptes(page, newpage); > - else > + } else > newpage->mapping = NULL; > > unlock_page(newpage); > @@ -619,6 +620,7 @@ static int unmap_and_move(new_page_t get > int *result = NULL; > struct page *newpage = get_new_page(page, private, &result); > int rcu_locked = 0; > + int charge = 0; > > if (!newpage) > return -ENOMEM; > @@ -660,14 +662,20 @@ static int unmap_and_move(new_page_t get > */ > if (!page->mapping) > goto rcu_unlock; > + > + charge = mem_cgroup_prepare_migration(page); > /* Establish migration ptes or remove ptes */ > try_to_unmap(page, 1); > > if (!page_mapped(page)) > rc = move_to_new_page(newpage, page); > > - if (rc) > + if (rc) { > remove_migration_ptes(page, page); > + if (charge) > + mem_cgroup_end_migration(page); > + } else if (charge) > + mem_cgroup_end_migration(newpage); > rcu_unlock: > if (rcu_locked) > rcu_read_unlock(); > Index: devel-2.6.23-rc8-mm2/include/linux/memcontrol.h > =================================================================== > --- devel-2.6.23-rc8-mm2.orig/include/linux/memcontrol.h > +++ devel-2.6.23-rc8-mm2/include/linux/memcontrol.h > @@ -56,6 +56,10 @@ static inline void mem_cgroup_uncharge_p > mem_cgroup_uncharge(page_get_page_cgroup(page)); > } > > +extern int mem_cgroup_prepare_migration(struct page *page); > +extern void mem_cgroup_end_migration(struct page *page); > +extern void mem_cgroup_page_migration(struct page *page, struct page *newpage); > + > #else /* CONFIG_CGROUP_MEM_CONT */ > static inline void mm_init_cgroup(struct mm_struct *mm, > struct task_struct *p) > @@ -107,6 +111,21 @@ static inline struct mem_cgroup *mm_cgro > return NULL; > } > > +static inline int mem_cgroup_prepare_migration(struct page *page) > +{ > + return 0; > +} > + > +static inline void mem_cgroup_end_migration(struct page *page) > +{ > +} > + > +static inline void > +mem_cgroup_page_migration(struct page *page, struct page *newpage); > +{ > +} > + > + > #endif /* CONFIG_CGROUP_MEM_CONT */ > > #endif /* _LINUX_MEMCONTROL_H */ > Index: devel-2.6.23-rc8-mm2/mm/memcontrol.c > =================================================================== > --- devel-2.6.23-rc8-mm2.orig/mm/memcontrol.c > +++ devel-2.6.23-rc8-mm2/mm/memcontrol.c > @@ -463,6 +463,49 @@ void mem_cgroup_uncharge(struct page_cgr > } > } > } > +/* > + * Returns non-zero if a page (under migration) has valid page_cgroup member. > + * Refcnt of page_cgroup is incremented. > + */ > + > +int mem_cgroup_prepare_migration(struct page *page) > +{ > + struct page_cgroup *pc; > + int ret = 0; > + lock_page_cgroup(page); > + pc = page_get_page_cgroup(page); > + if (pc && atomic_inc_not_zero(&pc->ref_cnt)) > + ret = 1; > + unlock_page_cgroup(page); > + return ret; > +} > + > +void mem_cgroup_end_migration(struct page *page) > +{ > + struct page_cgroup *pc = page_get_page_cgroup(page); > + mem_cgroup_uncharge(pc); > +} > +/* > + * We know both *page* and *newpage* are now not-on-LRU and Pg_locked. > + * And no rece with uncharge() routines becasue page_cgroup for *page* > + * has extra one reference by mem_cgroup_prepare_migration. > + */ > + > +void mem_cgroup_page_migration(struct page *page, struct page *newpage) > +{ > + struct page_cgroup *pc; > +retry: > + pc = page_get_page_cgroup(page); > + if (!pc) > + return; > + if (clear_page_cgroup(page, pc) != pc) > + goto retry; > + pc->page = newpage; > + lock_page_cgroup(newpage); > + page_assign_page_cgroup(newpage, pc); > + unlock_page_cgroup(newpage); > + return; > +} > > int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp) > { > Looks good to me Acked-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers