From e8589cc189f96b87348ae83ea4db38eaac624135 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Fri, 25 Jul 2008 01:47:10 -0700 Subject: [PATCH] memcg: better migration handling This patch changes page migration under memory controller to use a different algorithm. (thanks to Christoph for new idea.) Before: - page_cgroup is migrated from an old page to a new page. After: - a new page is accounted , no reuse of page_cgroup. Pros: - We can avoid compliated lock depndencies and races in migration. Cons: - new param to mem_cgroup_charge_common(). - mem_cgroup_getref() is added for handling ref_cnt ping-pong. This version simplifies complicated lock dependency in page migraiton under memory resource controller. new refcnt sequence is following. a mapped page: prepage_migration() ..... +1 to NEW page try_to_unmap() ..... all refs to OLD page is gone. move_pages() ..... +1 to NEW page if page cache. remap... ..... all refs from *map* is added to NEW one. end_migration() ..... -1 to New page. page's mapcount + (page_is_cache) refs are added to NEW one. Signed-off-by: KAMEZAWA Hiroyuki Cc: Balbir Singh Cc: Pavel Emelyanov Cc: Li Zefan Cc: YAMAMOTO Takashi Cc: Hugh Dickins Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 11 ++-- mm/memcontrol.c | 128 +++++++++++++++++++------------------ mm/migrate.c | 22 +++++-- 3 files changed, 86 insertions(+), 75 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index e6608776bc9..84ead2aa6f1 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -50,9 +50,10 @@ extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p); #define mm_match_cgroup(mm, cgroup) \ ((cgroup) == mem_cgroup_from_task((mm)->owner)) -extern int mem_cgroup_prepare_migration(struct page *page); +extern int +mem_cgroup_prepare_migration(struct page *page, struct page *newpage); extern void mem_cgroup_end_migration(struct page *page); -extern void mem_cgroup_page_migration(struct page *page, struct page *newpage); +extern int mem_cgroup_getref(struct page *page); /* * For memory reclaim. @@ -112,7 +113,8 @@ static inline int task_in_mem_cgroup(struct task_struct *task, return 1; } -static inline int mem_cgroup_prepare_migration(struct page *page) +static inline int +mem_cgroup_prepare_migration(struct page *page, struct page *newpage) { return 0; } @@ -121,8 +123,7 @@ static inline void mem_cgroup_end_migration(struct page *page) { } -static inline void -mem_cgroup_page_migration(struct page *page, struct page *newpage) +static inline void mem_cgroup_getref(struct page *page) { } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 90ccc132635..da5912b8455 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -524,7 +524,8 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan, * < 0 if the cgroup is over its limit */ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm, - gfp_t gfp_mask, enum charge_type ctype) + gfp_t gfp_mask, enum charge_type ctype, + struct mem_cgroup *memcg) { struct mem_cgroup *mem; struct page_cgroup *pc; @@ -569,16 +570,21 @@ retry: * thread group leader migrates. It's possible that mm is not * set, if so charge the init_mm (happens for pagecache usage). */ - if (!mm) - mm = &init_mm; + if (!memcg) { + if (!mm) + mm = &init_mm; - rcu_read_lock(); - mem = mem_cgroup_from_task(rcu_dereference(mm->owner)); - /* - * For every charge from the cgroup, increment reference count - */ - css_get(&mem->css); - rcu_read_unlock(); + rcu_read_lock(); + mem = mem_cgroup_from_task(rcu_dereference(mm->owner)); + /* + * For every charge from the cgroup, increment reference count + */ + css_get(&mem->css); + rcu_read_unlock(); + } else { + mem = memcg; + css_get(&memcg->css); + } while (res_counter_charge(&mem->res, PAGE_SIZE)) { if (!(gfp_mask & __GFP_WAIT)) @@ -648,7 +654,7 @@ err: int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask) { return mem_cgroup_charge_common(page, mm, gfp_mask, - MEM_CGROUP_CHARGE_TYPE_MAPPED); + MEM_CGROUP_CHARGE_TYPE_MAPPED, NULL); } int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm, @@ -657,7 +663,22 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm, if (!mm) mm = &init_mm; return mem_cgroup_charge_common(page, mm, gfp_mask, - MEM_CGROUP_CHARGE_TYPE_CACHE); + MEM_CGROUP_CHARGE_TYPE_CACHE, NULL); +} + +int mem_cgroup_getref(struct page *page) +{ + struct page_cgroup *pc; + + if (mem_cgroup_subsys.disabled) + return 0; + + lock_page_cgroup(page); + pc = page_get_page_cgroup(page); + VM_BUG_ON(!pc); + pc->ref_cnt++; + unlock_page_cgroup(page); + return 0; } /* @@ -707,65 +728,39 @@ unlock: } /* - * Returns non-zero if a page (under migration) has valid page_cgroup member. - * Refcnt of page_cgroup is incremented. + * Before starting migration, account against new page. */ -int mem_cgroup_prepare_migration(struct page *page) +int mem_cgroup_prepare_migration(struct page *page, struct page *newpage) { struct page_cgroup *pc; + struct mem_cgroup *mem = NULL; + enum charge_type ctype = MEM_CGROUP_CHARGE_TYPE_MAPPED; + int ret = 0; if (mem_cgroup_subsys.disabled) return 0; lock_page_cgroup(page); pc = page_get_page_cgroup(page); - if (pc) - pc->ref_cnt++; + if (pc) { + mem = pc->mem_cgroup; + css_get(&mem->css); + if (pc->flags & PAGE_CGROUP_FLAG_CACHE) + ctype = MEM_CGROUP_CHARGE_TYPE_CACHE; + } unlock_page_cgroup(page); - return pc != NULL; -} - -void mem_cgroup_end_migration(struct page *page) -{ - mem_cgroup_uncharge_page(page); + if (mem) { + ret = mem_cgroup_charge_common(newpage, NULL, GFP_KERNEL, + ctype, mem); + css_put(&mem->css); + } + return ret; } -/* - * We know both *page* and *newpage* are now not-on-LRU and PG_locked. - * And no race with uncharge() routines because page_cgroup for *page* - * has extra one reference by mem_cgroup_prepare_migration. - */ -void mem_cgroup_page_migration(struct page *page, struct page *newpage) +/* remove redundant charge */ +void mem_cgroup_end_migration(struct page *newpage) { - struct page_cgroup *pc; - struct mem_cgroup_per_zone *mz; - unsigned long flags; - - lock_page_cgroup(page); - pc = page_get_page_cgroup(page); - if (!pc) { - unlock_page_cgroup(page); - return; - } - - mz = page_cgroup_zoneinfo(pc); - spin_lock_irqsave(&mz->lru_lock, flags); - __mem_cgroup_remove_list(mz, pc); - spin_unlock_irqrestore(&mz->lru_lock, flags); - - page_assign_page_cgroup(page, NULL); - unlock_page_cgroup(page); - - pc->page = newpage; - lock_page_cgroup(newpage); - page_assign_page_cgroup(newpage, pc); - - mz = page_cgroup_zoneinfo(pc); - spin_lock_irqsave(&mz->lru_lock, flags); - __mem_cgroup_add_list(mz, pc); - spin_unlock_irqrestore(&mz->lru_lock, flags); - - unlock_page_cgroup(newpage); + mem_cgroup_uncharge_page(newpage); } /* @@ -795,12 +790,19 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *mem, page = pc->page; get_page(page); spin_unlock_irqrestore(&mz->lru_lock, flags); - mem_cgroup_uncharge_page(page); - put_page(page); - if (--count <= 0) { - count = FORCE_UNCHARGE_BATCH; + /* + * Check if this page is on LRU. !LRU page can be found + * if it's under page migration. + */ + if (PageLRU(page)) { + mem_cgroup_uncharge_page(page); + put_page(page); + if (--count <= 0) { + count = FORCE_UNCHARGE_BATCH; + cond_resched(); + } + } else cond_resched(); - } spin_lock_irqsave(&mz->lru_lock, flags); } spin_unlock_irqrestore(&mz->lru_lock, flags); diff --git a/mm/migrate.c b/mm/migrate.c index 376cceba82f..f6d7f8efd1a 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -358,6 +358,10 @@ static int migrate_page_move_mapping(struct address_space *mapping, __inc_zone_page_state(newpage, NR_FILE_PAGES); write_unlock_irq(&mapping->tree_lock); + if (!PageSwapCache(newpage)) { + mem_cgroup_uncharge_page(page); + mem_cgroup_getref(newpage); + } return 0; } @@ -611,7 +615,6 @@ static int move_to_new_page(struct page *newpage, struct page *page) rc = fallback_migrate_page(mapping, newpage, page); if (!rc) { - mem_cgroup_page_migration(page, newpage); remove_migration_ptes(page, newpage); } else newpage->mapping = NULL; @@ -641,6 +644,14 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, /* page was freed from under us. So we are done. */ goto move_newpage; + charge = mem_cgroup_prepare_migration(page, newpage); + if (charge == -ENOMEM) { + rc = -ENOMEM; + goto move_newpage; + } + /* prepare cgroup just returns 0 or -ENOMEM */ + BUG_ON(charge); + rc = -EAGAIN; if (TestSetPageLocked(page)) { if (!force) @@ -692,19 +703,14 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 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(); @@ -725,6 +731,8 @@ unlock: } move_newpage: + if (!charge) + mem_cgroup_end_migration(newpage); /* * Move the new page to the LRU. If migration was not successful * then this will free the page. -- 2.41.1