From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 641C26B004D for ; Wed, 18 Mar 2009 10:17:50 -0400 (EDT) Date: Wed, 18 Mar 2009 23:17:38 +0900 From: Daisuke Nishimura Subject: Re: [PATCH] fix unused/stale swap cache handling on memcg v1 (Re: [RFC] memcg: handle swapcache leak Message-Id: <20090318231738.4e042cbd.d-nishimura@mtf.biglobe.ne.jp> In-Reply-To: <20090318175734.f5a8a446.kamezawa.hiroyu@jp.fujitsu.com> References: <20090317135702.4222e62e.nishimura@mxp.nes.nec.co.jp> <20090317143903.a789cf57.kamezawa.hiroyu@jp.fujitsu.com> <20090317151113.79a3cc9d.nishimura@mxp.nes.nec.co.jp> <20090317162950.70c1245c.kamezawa.hiroyu@jp.fujitsu.com> <20090317183850.67c35b27.kamezawa.hiroyu@jp.fujitsu.com> <20090318101727.f00dfc2f.nishimura@mxp.nes.nec.co.jp> <20090318103418.7d38dce0.kamezawa.hiroyu@jp.fujitsu.com> <20090318125154.f8ffe652.nishimura@mxp.nes.nec.co.jp> <20090318175734.f5a8a446.kamezawa.hiroyu@jp.fujitsu.com> Reply-To: nishimura@mxp.nes.nec.co.jp Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: linux-mm , Balbir Singh , Hugh Dickins , d-nishimura@mtf.biglobe.ne.jp, Daisuke Nishimura List-ID: On Wed, 18 Mar 2009 17:57:34 +0900 KAMEZAWA Hiroyuki wrote: > How about this ? I did short test and this eems to work well. > I'm glad if you share us your test method. > (Hopefully, update memcg_debug.txt ;) > s/memcg_debug/memcg_test/ ? I don't do anything special not in the document. I just do one (or combination) of them for a long time and repeatedly, and observe what happens. > Changes: > - modified condition to trigger reclaim orphan paes. > > If I get good answer, I'll repost this with CC: to Andrew. > It looks good to me. Unfortunately, I don't have enough time tomorrow. I'll test this during this weekend and report the result in next week. Thanks, Daisuke Nishimura. > == > From: KAMEZAWA Hiroyuki > > Nishimura reported unused-swap-cache is not reclaimed well under memcg. > > Assume that memory cgroup well limits the memory usage of all applications > and file caches, and global-LRU-scan (kswapd() etc..) never runs. > > First, there is *allowed* race to SwapCache on global LRU. There can be > SwapCaches on global LRU, even when swp_entry is not referred by anyone(ptes). > When global LRU scan runs, it will be reclaimed by try_to_free_swap(). > But, they will not appear in memcg's private LRU and never reclaimed by > memcg's reclaim routines. > > Second, there are readahead SwapCaches, some of then tend to be not used > and reclaimed by global LRU when scan runs, at last. But they are not on > memcg's private LRU and will not be reclaimed until global-lru-scan runs. > > From memcg's point of view, above 2 is not very good. Especially, *unused* > swp_entry adds pressure to memcg's mem+swap controller and finally cause OOM. > (Nishimura confirmed this can cause OOM.) > > This patch tries to reclaim unused-swapcache by > - add a list for unused-swapcache (orphan_list) > - try to recalim orhan list by some threshold. > > Reported-by: Daisuke Nishimura > Signed-off-by: KAMEZAWA Hiroyuki > --- > include/linux/page_cgroup.h | 13 +++ > mm/memcontrol.c | 185 +++++++++++++++++++++++++++++++++++++++++++- > 2 files changed, 197 insertions(+), 1 deletion(-) > > Index: mmotm-2.6.29-Mar13/include/linux/page_cgroup.h > =================================================================== > --- mmotm-2.6.29-Mar13.orig/include/linux/page_cgroup.h > +++ mmotm-2.6.29-Mar13/include/linux/page_cgroup.h > @@ -26,6 +26,7 @@ enum { > PCG_LOCK, /* page cgroup is locked */ > PCG_CACHE, /* charged as cache */ > PCG_USED, /* this object is in use. */ > + PCG_ORPHAN, /* this is not used from memcg:s view but on global LRU */ > }; > > #define TESTPCGFLAG(uname, lname) \ > @@ -40,12 +41,24 @@ static inline void SetPageCgroup##uname( > static inline void ClearPageCgroup##uname(struct page_cgroup *pc) \ > { clear_bit(PCG_##lname, &pc->flags); } > > +#define TESTSETPCGFLAG(uname, lname) \ > +static inline int TestSetPageCgroup##uname(struct page_cgroup *pc) \ > + { return test_and_set_bit(PCG_##lname, &pc->flags); } > + > +#define TESTCLEARPCGFLAG(uname, lname) \ > +static inline int TestClearPageCgroup##uname(struct page_cgroup *pc) \ > + { return test_and_clear_bit(PCG_##lname, &pc->flags); } > + > /* Cache flag is set only once (at allocation) */ > TESTPCGFLAG(Cache, CACHE) > > TESTPCGFLAG(Used, USED) > CLEARPCGFLAG(Used, USED) > > +TESTPCGFLAG(Orphan, ORPHAN) > +TESTSETPCGFLAG(Orphan, ORPHAN) > +TESTCLEARPCGFLAG(Orphan, ORPHAN) > + > static inline int page_cgroup_nid(struct page_cgroup *pc) > { > return page_to_nid(pc->page); > Index: mmotm-2.6.29-Mar13/mm/memcontrol.c > =================================================================== > --- mmotm-2.6.29-Mar13.orig/mm/memcontrol.c > +++ mmotm-2.6.29-Mar13/mm/memcontrol.c > @@ -371,6 +371,61 @@ static int mem_cgroup_walk_tree(struct m > * When moving account, the page is not on LRU. It's isolated. > */ > > +/* > + * Orphan List is a list for page_cgroup which is not free but not under > + * any cgroup. SwapCache which is prefetched by readahead() is typical type but > + * there are other corner cases. > + * > + * Usually, updates to this list happens when swap cache is readaheaded and > + * finally used by process. > + */ > + > +/* for orphan page_cgroups, updated under zone->lru_lock. */ > + > +struct orphan_list_node { > + struct orphan_list_zone { > + int event; > + struct list_head list; > + } zone[MAX_NR_ZONES]; > +}; > +struct orphan_list_node *orphan_list[MAX_NUMNODES] __read_mostly; > +#define ORPHAN_EVENT_THRESH (256) > +static void check_orphan_stat(void); > +atomic_t nr_orphan_caches; > + > +static inline struct orphan_list_zone *orphan_lru(int nid, int zid) > +{ > + /* > + * 2 cases for this BUG_ON(), swapcache is generated while init. > + * or NID should be invalid. > + */ > + BUG_ON(!orphan_list[nid]); > + return &orphan_list[nid]->zone[zid]; > +} > + > +static inline void remove_orphan_list(struct page_cgroup *pc) > +{ > + if (TestClearPageCgroupOrphan(pc)) { > + list_del_init(&pc->lru); > + atomic_dec(&nr_orphan_caches); > + } > +} > + > +static void add_orphan_list(struct page *page, struct page_cgroup *pc) > +{ > + if (TestSetPageCgroupOrphan(pc)) { > + struct orphan_list_zone *opl; > + opl = orphan_lru(page_to_nid(page), page_zonenum(page)); > + list_add_tail(&pc->lru, &opl->list); > + atomic_inc(&nr_orphan_caches); > + if (opl->event++ > ORPHAN_EVENT_THRESH) { > + check_orphan_stat(); > + opl->event = 0; > + } > + } > +} > + > + > void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru) > { > struct page_cgroup *pc; > @@ -380,6 +435,14 @@ void mem_cgroup_del_lru_list(struct page > if (mem_cgroup_disabled()) > return; > pc = lookup_page_cgroup(page); > + /* > + * If the page is SwapCache and already on global LRU, it will be on > + * orphan list. remove here > + */ > + if (unlikely(PageCgroupOrphan(pc))) { > + remove_orphan_list(pc); > + return; > + } > /* can happen while we handle swapcache. */ > if (list_empty(&pc->lru) || !pc->mem_cgroup) > return; > @@ -433,8 +496,11 @@ void mem_cgroup_add_lru_list(struct page > * For making pc->mem_cgroup visible, insert smp_rmb() here. > */ > smp_rmb(); > - if (!PageCgroupUsed(pc)) > + if (!PageCgroupUsed(pc)) { > + /* handle swap cache here */ > + add_orphan_list(page, pc); > return; > + } > > mz = page_cgroup_zoneinfo(pc); > MEM_CGROUP_ZSTAT(mz, lru) += 1; > @@ -471,6 +537,9 @@ static void mem_cgroup_lru_add_after_com > struct page_cgroup *pc = lookup_page_cgroup(page); > > spin_lock_irqsave(&zone->lru_lock, flags); > + if (PageCgroupOrphan(pc)) > + remove_orphan_list(pc); > + > /* link when the page is linked to LRU but page_cgroup isn't */ > if (PageLRU(page) && list_empty(&pc->lru)) > mem_cgroup_add_lru_list(page, page_lru(page)); > @@ -784,6 +853,119 @@ static int mem_cgroup_count_children(str > return num; > } > > + > + > +/* > + * Using big number here for avoiding to free orphan swap-cache by readahead > + * We don't want to delete swap caches read by readahead. > + */ > +static int orphan_thresh(void) > +{ > + int nr_pages = (1 << page_cluster); /* max size of a swap readahead */ > + int base = num_online_cpus() * 256; /* 1M per cpu if swap is 4k */ > + > + nr_pages *= nr_threads/2; /* nr_threads can be too big, too small */ > + > + /* too small value will kill readahead */ > + if (nr_pages < base) > + return base; > + > + /* too big is not suitable here */ > + if (nr_pages > base * 4) > + return base * 4; > + > + return nr_pages; > +} > + > +/* > + * In usual, *unused* swap cache are reclaimed by global LRU. But, if no one > + * kicks global LRU, they will not be reclaimed. When using memcg, it's trouble. > + */ > +static int drain_orphan_swapcaches(int nid, int zid) > +{ > + struct page_cgroup *pc; > + struct zone *zone; > + struct page *page; > + struct orphan_list_zone *lru = orphan_lru(nid, zid); > + unsigned long flags; > + int drain, scan; > + > + zone = &NODE_DATA(nid)->node_zones[zid]; > + /* check one by one */ > + scan = 0; > + drain = 0; > + spin_lock_irqsave(&zone->lru_lock, flags); > + while (!list_empty(&lru->list) && (scan < SWAP_CLUSTER_MAX*2)) { > + scan++; > + pc = list_entry(lru->list.next, struct page_cgroup, lru); > + page = pc->page; > + /* Rotate */ > + list_del(&pc->lru); > + list_add_tail(&pc->lru, &lru->list); > + /* get page for isolate_lru_page() */ > + if (get_page_unless_zero(page)) { > + spin_unlock_irqrestore(&zone->lru_lock, flags); > + if (!isolate_lru_page(page)) { > + /* Now, This page is removed from LRU */ > + if (trylock_page(page)) { > + drain += try_to_free_swap(page); > + unlock_page(page); > + } > + putback_lru_page(page); > + } > + put_page(page); > + spin_lock_irqsave(&zone->lru_lock, flags); > + } > + } > + spin_unlock_irqrestore(&zone->lru_lock, flags); > + > + return drain; > +} > + > +/* access without lock...serialization is not so important here. */ > +static int last_visit; > +void try_delete_orphan_caches(struct work_struct *work) > +{ > + int nid, zid, drain; > + > + nid = last_visit; > + drain = 0; > + while (drain < SWAP_CLUSTER_MAX) { > + nid = next_node(nid, node_states[N_HIGH_MEMORY]); > + if (nid == MAX_NUMNODES) > + nid = 0; > + last_visit = nid; > + if (node_state(nid, N_HIGH_MEMORY)) > + for (zid = 0; zid < MAX_NR_ZONES; zid++) > + drain += drain_orphan_swapcaches(nid, zid); > + if (nid == 0) > + break; > + } > +} > +DECLARE_WORK(orphan_delete_work, try_delete_orphan_caches); > + > +static void check_orphan_stat(void) > +{ > + if (atomic_read(&nr_orphan_caches) > orphan_thresh()) > + schedule_work(&orphan_delete_work); > +} > + > +static __init void init_orphan_lru(void) > +{ > + struct orphan_list_node *opl; > + int nid, zid; > + > + for_each_node_state(nid, N_POSSIBLE) { > + opl = kmalloc(sizeof(struct orphan_list_node), GFP_KERNEL); > + BUG_ON(!opl); > + for (zid = 0; zid < MAX_NR_ZONES; zid++) { > + INIT_LIST_HEAD(&opl->zone[zid].list); > + opl->zone[zid].event = 0; > + } > + orphan_list[nid] = opl; > + } > +} > + > /* > * Visit the first child (need not be the first child as per the ordering > * of the cgroup list, since we track last_scanned_child) of @mem and use > @@ -2454,6 +2636,7 @@ mem_cgroup_create(struct cgroup_subsys * > /* root ? */ > if (cont->parent == NULL) { > enable_swap_cgroup(); > + init_orphan_lru(); > parent = NULL; > } else { > parent = mem_cgroup_from_cont(cont->parent); > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org