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Message-Id: <20081031182530.f4bd80be.nishimura@mxp.nes.nec.co.jp> Date: Fri, 31 Oct 2008 18:25:30 +0900 From: Daisuke Nishimura <nishimura@....nes.nec.co.jp> To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>, "nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>, hugh@...itas.com, taka@...inux.co.jp Subject: Re: [RFC][PATCH 1/5] memcg : force_empty to do move account On Fri, 31 Oct 2008 11:52:41 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote: > This patch provides a function to move account information of a page between > mem_cgroups and rewrite force_empty to make use of this. > > This moving of page_cgroup is done under > - lru_lock of source/destination mem_cgroup is held. > - lock_page_cgroup() is held. > > Then, a routine which touches pc->mem_cgroup without lock_page_cgroup() should > confirm pc->mem_cgroup is still valid or not. Typical code can be following. > > (while page is not under lock_page()) > mem = pc->mem_cgroup; > mz = page_cgroup_zoneinfo(pc) > spin_lock_irqsave(&mz->lru_lock); > if (pc->mem_cgroup == mem) > ...../* some list handling */ > spin_unlock_irqrestore(&mz->lru_lock); > > Of course, better way is > lock_page_cgroup(pc); > .... > unlock_page_cgroup(pc); > > But you should confirm the nest of lock and avoid deadlock. > > If you treats page_cgroup from mem_cgroup's LRU under mz->lru_lock, > you don't have to worry about what pc->mem_cgroup points to. > moved pages are added to head of lru, not to tail. > > Expected users of this routine is: > - force_empty (rmdir) > - moving tasks between cgroup (for moving account information.) > - hierarchy (maybe useful.) > > force_empty(rmdir) uses this move_account and move pages to its parent. > This "move" will not cause OOM (I added "oom" parameter to try_charge().) > > If the parent is busy (not enough memory), force_empty calls try_to_free_page() > and reduce usage. > > Purpose of this behavior is > - Fix "forget all" behavior of force_empty and avoid leak of accounting. > - By "moving first, free if necessary", keep pages on memory as much as > possible. > > Adding a switch to change behavior of force_empty to > - free first, move if necessary > - free all, if there is mlocked/busy pages, return -EBUSY. > is under consideration. > > This patch removes memory.force_empty file, a brutal debug-only interface. > > Changelog: (v8) -> (v9) > - fixed typos. > > Changelog: (v6) -> (v8) > - removed memory.force_empty file which was provided only for debug. > > Changelog: (v5) -> (v6) > - removed unnecessary check. > - do all under lock_page_cgroup(). > - removed res_counter_charge() from move function itself. > (and modifies try_charge() function.) > - add argument to add_list() to specify to add page_cgroup head or tail. > - merged with force_empty patch. (to answer who is user? question) > > Changelog: (v4) -> (v5) > - check for lock_page() is removed. > - rewrote description. > > Changelog: (v2) -> (v4) > - added lock_page_cgroup(). > - moved out from new-force-empty patch. > - added how-to-use text. > - fixed race in __mem_cgroup_uncharge_common(). > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> > Previous version(v8) of this patch worked well under my rmdir test for more than 24 hours, and there is no practical difference from then. (I tested this version too for a few hours just to make sure.) Reviewed-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp> Tested-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp> Thanks, Daisuke Nishimura. > Documentation/controllers/memory.txt | 12 - > mm/memcontrol.c | 277 ++++++++++++++++++++++++++--------- > 2 files changed, 214 insertions(+), 75 deletions(-) > > Index: mmotm-2.6.28-rc2+/mm/memcontrol.c > =================================================================== > --- mmotm-2.6.28-rc2+.orig/mm/memcontrol.c > +++ mmotm-2.6.28-rc2+/mm/memcontrol.c > @@ -257,7 +257,7 @@ static void __mem_cgroup_remove_list(str > } > > static void __mem_cgroup_add_list(struct mem_cgroup_per_zone *mz, > - struct page_cgroup *pc) > + struct page_cgroup *pc, bool hot) > { > int lru = LRU_BASE; > > @@ -271,7 +271,10 @@ static void __mem_cgroup_add_list(struct > } > > MEM_CGROUP_ZSTAT(mz, lru) += 1; > - list_add(&pc->lru, &mz->lists[lru]); > + if (hot) > + list_add(&pc->lru, &mz->lists[lru]); > + else > + list_add_tail(&pc->lru, &mz->lists[lru]); > > mem_cgroup_charge_statistics(pc->mem_cgroup, pc, true); > } > @@ -467,21 +470,12 @@ unsigned long mem_cgroup_isolate_pages(u > return nr_taken; > } > > - > -/** > - * mem_cgroup_try_charge - get charge of PAGE_SIZE. > - * @mm: an mm_struct which is charged against. (when *memcg is NULL) > - * @gfp_mask: gfp_mask for reclaim. > - * @memcg: a pointer to memory cgroup which is charged against. > - * > - * charge against memory cgroup pointed by *memcg. if *memcg == NULL, estimated > - * memory cgroup from @mm is got and stored in *memcg. > - * > - * Returns 0 if success. -ENOMEM at failure. > +/* > + * Unlike exported interface, "oom" parameter is added. if oom==true, > + * oom-killer can be invoked. > */ > - > -int mem_cgroup_try_charge(struct mm_struct *mm, > - gfp_t gfp_mask, struct mem_cgroup **memcg) > +static int __mem_cgroup_try_charge(struct mm_struct *mm, > + gfp_t gfp_mask, struct mem_cgroup **memcg, bool oom) > { > struct mem_cgroup *mem; > int nr_retries = MEM_CGROUP_RECLAIM_RETRIES; > @@ -528,7 +522,8 @@ int mem_cgroup_try_charge(struct mm_stru > continue; > > if (!nr_retries--) { > - mem_cgroup_out_of_memory(mem, gfp_mask); > + if (oom) > + mem_cgroup_out_of_memory(mem, gfp_mask); > goto nomem; > } > } > @@ -538,6 +533,25 @@ nomem: > return -ENOMEM; > } > > +/** > + * mem_cgroup_try_charge - get charge of PAGE_SIZE. > + * @mm: an mm_struct which is charged against. (when *memcg is NULL) > + * @gfp_mask: gfp_mask for reclaim. > + * @memcg: a pointer to memory cgroup which is charged against. > + * > + * charge against memory cgroup pointed by *memcg. if *memcg == NULL, estimated > + * memory cgroup from @mm is got and stored in *memcg. > + * > + * Returns 0 if success. -ENOMEM at failure. > + * This call can invoke OOM-Killer. > + */ > + > +int mem_cgroup_try_charge(struct mm_struct *mm, > + gfp_t mask, struct mem_cgroup **memcg) > +{ > + return __mem_cgroup_try_charge(mm, mask, memcg, true); > +} > + > /* > * commit a charge got by mem_cgroup_try_charge() and makes page_cgroup to be > * USED state. If already USED, uncharge and return. > @@ -571,11 +585,109 @@ static void __mem_cgroup_commit_charge(s > mz = page_cgroup_zoneinfo(pc); > > spin_lock_irqsave(&mz->lru_lock, flags); > - __mem_cgroup_add_list(mz, pc); > + __mem_cgroup_add_list(mz, pc, true); > spin_unlock_irqrestore(&mz->lru_lock, flags); > unlock_page_cgroup(pc); > } > > +/** > + * mem_cgroup_move_account - move account of the page > + * @pc: page_cgroup of the page. > + * @from: mem_cgroup which the page is moved from. > + * @to: mem_cgroup which the page is moved to. @from != @to. > + * > + * The caller must confirm following. > + * 1. disable irq. > + * 2. lru_lock of old mem_cgroup(@from) should be held. > + * > + * returns 0 at success, > + * returns -EBUSY when lock is busy or "pc" is unstable. > + * > + * This function does "uncharge" from old cgroup but doesn't do "charge" to > + * new cgroup. It should be done by a caller. > + */ > + > +static int mem_cgroup_move_account(struct page_cgroup *pc, > + struct mem_cgroup *from, struct mem_cgroup *to) > +{ > + struct mem_cgroup_per_zone *from_mz, *to_mz; > + int nid, zid; > + int ret = -EBUSY; > + > + VM_BUG_ON(!irqs_disabled()); > + VM_BUG_ON(from == to); > + > + nid = page_cgroup_nid(pc); > + zid = page_cgroup_zid(pc); > + from_mz = mem_cgroup_zoneinfo(from, nid, zid); > + to_mz = mem_cgroup_zoneinfo(to, nid, zid); > + > + > + if (!trylock_page_cgroup(pc)) > + return ret; > + > + if (!PageCgroupUsed(pc)) > + goto out; > + > + if (pc->mem_cgroup != from) > + goto out; > + > + if (spin_trylock(&to_mz->lru_lock)) { > + __mem_cgroup_remove_list(from_mz, pc); > + css_put(&from->css); > + res_counter_uncharge(&from->res, PAGE_SIZE); > + pc->mem_cgroup = to; > + css_get(&to->css); > + __mem_cgroup_add_list(to_mz, pc, false); > + ret = 0; > + spin_unlock(&to_mz->lru_lock); > + } > +out: > + unlock_page_cgroup(pc); > + return ret; > +} > + > +/* > + * move charges to its parent. > + */ > + > +static int mem_cgroup_move_parent(struct page_cgroup *pc, > + struct mem_cgroup *child, > + gfp_t gfp_mask) > +{ > + struct cgroup *cg = child->css.cgroup; > + struct cgroup *pcg = cg->parent; > + struct mem_cgroup *parent; > + struct mem_cgroup_per_zone *mz; > + unsigned long flags; > + int ret; > + > + /* Is ROOT ? */ > + if (!pcg) > + return -EINVAL; > + > + parent = mem_cgroup_from_cont(pcg); > + > + ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false); > + if (ret) > + return ret; > + > + mz = mem_cgroup_zoneinfo(child, > + page_cgroup_nid(pc), page_cgroup_zid(pc)); > + > + spin_lock_irqsave(&mz->lru_lock, flags); > + ret = mem_cgroup_move_account(pc, child, parent); > + spin_unlock_irqrestore(&mz->lru_lock, flags); > + > + /* drop extra refcnt */ > + css_put(&parent->css); > + /* uncharge if move fails */ > + if (ret) > + res_counter_uncharge(&parent->res, PAGE_SIZE); > + > + return ret; > +} > + > /* > * Charge the memory controller for page usage. > * Return > @@ -597,7 +709,7 @@ static int mem_cgroup_charge_common(stru > prefetchw(pc); > > mem = memcg; > - ret = mem_cgroup_try_charge(mm, gfp_mask, &mem); > + ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true); > if (ret) > return ret; > > @@ -898,46 +1010,52 @@ int mem_cgroup_resize_limit(struct mem_c > * This routine traverse page_cgroup in given list and drop them all. > * *And* this routine doesn't reclaim page itself, just removes page_cgroup. > */ > -#define FORCE_UNCHARGE_BATCH (128) > -static void mem_cgroup_force_empty_list(struct mem_cgroup *mem, > +static int mem_cgroup_force_empty_list(struct mem_cgroup *mem, > struct mem_cgroup_per_zone *mz, > enum lru_list lru) > { > - struct page_cgroup *pc; > - struct page *page; > - int count = FORCE_UNCHARGE_BATCH; > + struct page_cgroup *pc, *busy; > unsigned long flags; > + unsigned long loop; > struct list_head *list; > + int ret = 0; > > list = &mz->lists[lru]; > > - spin_lock_irqsave(&mz->lru_lock, flags); > - while (!list_empty(list)) { > - pc = list_entry(list->prev, struct page_cgroup, lru); > - page = pc->page; > - if (!PageCgroupUsed(pc)) > + loop = MEM_CGROUP_ZSTAT(mz, lru); > + /* give some margin against EBUSY etc...*/ > + loop += 256; > + busy = NULL; > + while (loop--) { > + ret = 0; > + spin_lock_irqsave(&mz->lru_lock, flags); > + if (list_empty(list)) { > + spin_unlock_irqrestore(&mz->lru_lock, flags); > break; > - get_page(page); > + } > + pc = list_entry(list->prev, struct page_cgroup, lru); > + if (busy == pc) { > + list_move(&pc->lru, list); > + busy = 0; > + spin_unlock_irqrestore(&mz->lru_lock, flags); > + continue; > + } > spin_unlock_irqrestore(&mz->lru_lock, flags); > - /* > - * Check if this page is on LRU. !LRU page can be found > - * if it's under page migration. > - */ > - if (PageLRU(page)) { > - __mem_cgroup_uncharge_common(page, > - MEM_CGROUP_CHARGE_TYPE_FORCE); > - put_page(page); > - if (--count <= 0) { > - count = FORCE_UNCHARGE_BATCH; > - cond_resched(); > - } > - } else { > - spin_lock_irqsave(&mz->lru_lock, flags); > + > + ret = mem_cgroup_move_parent(pc, mem, GFP_HIGHUSER_MOVABLE); > + if (ret == -ENOMEM) > break; > - } > - spin_lock_irqsave(&mz->lru_lock, flags); > + > + if (ret == -EBUSY || ret == -EINVAL) { > + /* found lock contention or "pc" is obsolete. */ > + busy = pc; > + cond_resched(); > + } else > + busy = NULL; > } > - spin_unlock_irqrestore(&mz->lru_lock, flags); > + if (!ret && !list_empty(list)) > + return -EBUSY; > + return ret; > } > > /* > @@ -946,34 +1064,68 @@ static void mem_cgroup_force_empty_list( > */ > static int mem_cgroup_force_empty(struct mem_cgroup *mem) > { > - int ret = -EBUSY; > - int node, zid; > + int ret; > + int node, zid, shrink; > + int nr_retries = MEM_CGROUP_RECLAIM_RETRIES; > > css_get(&mem->css); > - /* > - * page reclaim code (kswapd etc..) will move pages between > - * active_list <-> inactive_list while we don't take a lock. > - * So, we have to do loop here until all lists are empty. > - */ > + > + shrink = 0; > +move_account: > while (mem->res.usage > 0) { > + ret = -EBUSY; > if (atomic_read(&mem->css.cgroup->count) > 0) > goto out; > + > /* This is for making all *used* pages to be on LRU. */ > lru_add_drain_all(); > - for_each_node_state(node, N_POSSIBLE) > - for (zid = 0; zid < MAX_NR_ZONES; zid++) { > + ret = 0; > + for_each_node_state(node, N_POSSIBLE) { > + for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) { > struct mem_cgroup_per_zone *mz; > enum lru_list l; > mz = mem_cgroup_zoneinfo(mem, node, zid); > - for_each_lru(l) > - mem_cgroup_force_empty_list(mem, mz, l); > + for_each_lru(l) { > + ret = mem_cgroup_force_empty_list(mem, > + mz, l); > + if (ret) > + break; > + } > } > + if (ret) > + break; > + } > + /* it seems parent cgroup doesn't have enough mem */ > + if (ret == -ENOMEM) > + goto try_to_free; > cond_resched(); > } > ret = 0; > out: > css_put(&mem->css); > return ret; > + > +try_to_free: > + /* returns EBUSY if we come here twice. */ > + if (shrink) { > + ret = -EBUSY; > + goto out; > + } > + /* try to free all pages in this cgroup */ > + shrink = 1; > + while (nr_retries && mem->res.usage > 0) { > + int progress; > + progress = try_to_free_mem_cgroup_pages(mem, > + GFP_HIGHUSER_MOVABLE); > + if (!progress) > + nr_retries--; > + > + } > + /* try move_account...there may be some *locked* pages. */ > + if (mem->res.usage) > + goto move_account; > + ret = 0; > + goto out; > } > > static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft) > @@ -1022,11 +1174,6 @@ static int mem_cgroup_reset(struct cgrou > return 0; > } > > -static int mem_force_empty_write(struct cgroup *cont, unsigned int event) > -{ > - return mem_cgroup_force_empty(mem_cgroup_from_cont(cont)); > -} > - > static const struct mem_cgroup_stat_desc { > const char *msg; > u64 unit; > @@ -1103,10 +1250,6 @@ static struct cftype mem_cgroup_files[] > .read_u64 = mem_cgroup_read, > }, > { > - .name = "force_empty", > - .trigger = mem_force_empty_write, > - }, > - { > .name = "stat", > .read_map = mem_control_stat_show, > }, > Index: mmotm-2.6.28-rc2+/Documentation/controllers/memory.txt > =================================================================== > --- mmotm-2.6.28-rc2+.orig/Documentation/controllers/memory.txt > +++ mmotm-2.6.28-rc2+/Documentation/controllers/memory.txt > @@ -207,12 +207,6 @@ exceeded. > The memory.stat file gives accounting information. Now, the number of > caches, RSS and Active pages/Inactive pages are shown. > > -The memory.force_empty gives an interface to drop *all* charges by force. > - > -# echo 1 > memory.force_empty > - > -will drop all charges in cgroup. Currently, this is maintained for test. > - > 4. Testing > > Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11]. > @@ -242,8 +236,10 @@ reclaimed. > > A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a > cgroup might have some charge associated with it, even though all > -tasks have migrated away from it. Such charges are automatically dropped at > -rmdir() if there are no tasks. > +tasks have migrated away from it. > +Such charges are moved to its parent as much as possible and freed if parent > +is full. > +If both of them are busy, rmdir() returns -EBUSY. > > 5. TODO > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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