1 /* memcontrol.c - Memory Controller
3 * Copyright IBM Corporation, 2007
4 * Author Balbir Singh <balbir@linux.vnet.ibm.com>
6 * Copyright 2007 OpenVZ SWsoft Inc
7 * Author: Pavel Emelianov <xemul@openvz.org>
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
20 #include <linux/res_counter.h>
21 #include <linux/memcontrol.h>
22 #include <linux/cgroup.h>
24 #include <linux/page-flags.h>
25 #include <linux/backing-dev.h>
26 #include <linux/bit_spinlock.h>
27 #include <linux/rcupdate.h>
28 #include <linux/swap.h>
29 #include <linux/spinlock.h>
32 struct cgroup_subsys mem_cgroup_subsys;
33 static const int MEM_CGROUP_RECLAIM_RETRIES = 5;
36 * The memory controller data structure. The memory controller controls both
37 * page cache and RSS per cgroup. We would eventually like to provide
38 * statistics based on the statistics developed by Rik Van Riel for clock-pro,
39 * to help the administrator determine what knobs to tune.
41 * TODO: Add a water mark for the memory controller. Reclaim will begin when
42 * we hit the water mark. May be even add a low water mark, such that
43 * no reclaim occurs from a cgroup at it's low water mark, this is
44 * a feature that will be implemented much later in the future.
47 struct cgroup_subsys_state css;
49 * the counter to account for memory usage
51 struct res_counter res;
53 * Per cgroup active and inactive list, similar to the
55 * TODO: Consider making these lists per zone
57 struct list_head active_list;
58 struct list_head inactive_list;
60 * spin_lock to protect the per cgroup LRU
66 * We use the lower bit of the page->page_cgroup pointer as a bit spin
67 * lock. We need to ensure that page->page_cgroup is atleast two
68 * byte aligned (based on comments from Nick Piggin)
70 #define PAGE_CGROUP_LOCK_BIT 0x0
71 #define PAGE_CGROUP_LOCK (1 << PAGE_CGROUP_LOCK_BIT)
74 * A page_cgroup page is associated with every page descriptor. The
75 * page_cgroup helps us identify information about the cgroup
78 struct list_head lru; /* per cgroup LRU list */
80 struct mem_cgroup *mem_cgroup;
81 atomic_t ref_cnt; /* Helpful when pages move b/w */
82 /* mapped and cached states */
87 struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
89 return container_of(cgroup_subsys_state(cont,
90 mem_cgroup_subsys_id), struct mem_cgroup,
95 struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
97 return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
98 struct mem_cgroup, css);
101 void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p)
103 struct mem_cgroup *mem;
105 mem = mem_cgroup_from_task(p);
107 mm->mem_cgroup = mem;
110 void mm_free_cgroup(struct mm_struct *mm)
112 css_put(&mm->mem_cgroup->css);
115 static inline int page_cgroup_locked(struct page *page)
117 return bit_spin_is_locked(PAGE_CGROUP_LOCK_BIT,
121 void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
126 * While resetting the page_cgroup we might not hold the
127 * page_cgroup lock. free_hot_cold_page() is an example
131 VM_BUG_ON(!page_cgroup_locked(page));
132 locked = (page->page_cgroup & PAGE_CGROUP_LOCK);
133 page->page_cgroup = ((unsigned long)pc | locked);
136 struct page_cgroup *page_get_page_cgroup(struct page *page)
138 return (struct page_cgroup *)
139 (page->page_cgroup & ~PAGE_CGROUP_LOCK);
142 void __always_inline lock_page_cgroup(struct page *page)
144 bit_spin_lock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
145 VM_BUG_ON(!page_cgroup_locked(page));
148 void __always_inline unlock_page_cgroup(struct page *page)
150 bit_spin_unlock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
153 void __mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
156 list_move(&pc->lru, &pc->mem_cgroup->active_list);
158 list_move(&pc->lru, &pc->mem_cgroup->inactive_list);
162 * This routine assumes that the appropriate zone's lru lock is already held
164 void mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
166 struct mem_cgroup *mem;
170 mem = pc->mem_cgroup;
172 spin_lock(&mem->lru_lock);
173 __mem_cgroup_move_lists(pc, active);
174 spin_unlock(&mem->lru_lock);
177 unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
178 struct list_head *dst,
179 unsigned long *scanned, int order,
180 int mode, struct zone *z,
181 struct mem_cgroup *mem_cont,
184 unsigned long nr_taken = 0;
188 struct list_head *src;
189 struct page_cgroup *pc;
192 src = &mem_cont->active_list;
194 src = &mem_cont->inactive_list;
196 spin_lock(&mem_cont->lru_lock);
197 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
198 pc = list_entry(src->prev, struct page_cgroup, lru);
202 if (PageActive(page) && !active) {
203 __mem_cgroup_move_lists(pc, true);
207 if (!PageActive(page) && active) {
208 __mem_cgroup_move_lists(pc, false);
215 * TODO: make the active/inactive lists per zone
217 if (page_zone(page) != z)
221 * Check if the meta page went away from under us
223 if (!list_empty(&pc->lru))
224 list_move(&pc->lru, &pc_list);
228 if (__isolate_lru_page(page, mode) == 0) {
229 list_move(&page->lru, dst);
234 list_splice(&pc_list, src);
235 spin_unlock(&mem_cont->lru_lock);
242 * Charge the memory controller for page usage.
244 * 0 if the charge was successful
245 * < 0 if the cgroup is over its limit
247 int mem_cgroup_charge(struct page *page, struct mm_struct *mm)
249 struct mem_cgroup *mem;
250 struct page_cgroup *pc, *race_pc;
252 unsigned long nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
255 * Should page_cgroup's go to their own slab?
256 * One could optimize the performance of the charging routine
257 * by saving a bit in the page_flags and using it as a lock
258 * to see if the cgroup page already has a page_cgroup associated
262 lock_page_cgroup(page);
263 pc = page_get_page_cgroup(page);
265 * The page_cgroup exists and the page has already been accounted
268 if (unlikely(!atomic_inc_not_zero(&pc->ref_cnt))) {
269 /* this page is under being uncharged ? */
270 unlock_page_cgroup(page);
277 unlock_page_cgroup(page);
279 pc = kzalloc(sizeof(struct page_cgroup), GFP_KERNEL);
285 * We always charge the cgroup the mm_struct belongs to
286 * the mm_struct's mem_cgroup changes on task migration if the
287 * thread group leader migrates. It's possible that mm is not
288 * set, if so charge the init_mm (happens for pagecache usage).
293 mem = rcu_dereference(mm->mem_cgroup);
295 * For every charge from the cgroup, increment reference
302 * If we created the page_cgroup, we should free it on exceeding
305 while (res_counter_charge(&mem->res, 1)) {
306 if (try_to_free_mem_cgroup_pages(mem))
310 * try_to_free_mem_cgroup_pages() might not give us a full
311 * picture of reclaim. Some pages are reclaimed and might be
312 * moved to swap cache or just unmapped from the cgroup.
313 * Check the limit again to see if the reclaim reduced the
314 * current usage of the cgroup before giving up
316 if (res_counter_check_under_limit(&mem->res))
319 * Since we control both RSS and cache, we end up with a
320 * very interesting scenario where we end up reclaiming
321 * memory (essentially RSS), since the memory is pushed
322 * to swap cache, we eventually end up adding those
323 * pages back to our list. Hence we give ourselves a
324 * few chances before we fail
326 else if (nr_retries--) {
327 congestion_wait(WRITE, HZ/10);
335 lock_page_cgroup(page);
337 * Check if somebody else beat us to allocating the page_cgroup
339 race_pc = page_get_page_cgroup(page);
343 atomic_inc(&pc->ref_cnt);
344 res_counter_uncharge(&mem->res, 1);
349 atomic_set(&pc->ref_cnt, 1);
350 pc->mem_cgroup = mem;
352 page_assign_page_cgroup(page, pc);
354 spin_lock_irqsave(&mem->lru_lock, flags);
355 list_add(&pc->lru, &mem->active_list);
356 spin_unlock_irqrestore(&mem->lru_lock, flags);
359 unlock_page_cgroup(page);
368 * Uncharging is always a welcome operation, we never complain, simply
371 void mem_cgroup_uncharge(struct page_cgroup *pc)
373 struct mem_cgroup *mem;
380 if (atomic_dec_and_test(&pc->ref_cnt)) {
382 lock_page_cgroup(page);
383 mem = pc->mem_cgroup;
385 page_assign_page_cgroup(page, NULL);
386 unlock_page_cgroup(page);
387 res_counter_uncharge(&mem->res, 1);
389 spin_lock_irqsave(&mem->lru_lock, flags);
390 list_del_init(&pc->lru);
391 spin_unlock_irqrestore(&mem->lru_lock, flags);
396 static ssize_t mem_cgroup_read(struct cgroup *cont, struct cftype *cft,
397 struct file *file, char __user *userbuf, size_t nbytes,
400 return res_counter_read(&mem_cgroup_from_cont(cont)->res,
401 cft->private, userbuf, nbytes, ppos);
404 static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
405 struct file *file, const char __user *userbuf,
406 size_t nbytes, loff_t *ppos)
408 return res_counter_write(&mem_cgroup_from_cont(cont)->res,
409 cft->private, userbuf, nbytes, ppos);
412 static struct cftype mem_cgroup_files[] = {
415 .private = RES_USAGE,
416 .read = mem_cgroup_read,
420 .private = RES_LIMIT,
421 .write = mem_cgroup_write,
422 .read = mem_cgroup_read,
426 .private = RES_FAILCNT,
427 .read = mem_cgroup_read,
431 static struct mem_cgroup init_mem_cgroup;
433 static struct cgroup_subsys_state *
434 mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
436 struct mem_cgroup *mem;
438 if (unlikely((cont->parent) == NULL)) {
439 mem = &init_mem_cgroup;
440 init_mm.mem_cgroup = mem;
442 mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
447 res_counter_init(&mem->res);
448 INIT_LIST_HEAD(&mem->active_list);
449 INIT_LIST_HEAD(&mem->inactive_list);
450 spin_lock_init(&mem->lru_lock);
454 static void mem_cgroup_destroy(struct cgroup_subsys *ss,
457 kfree(mem_cgroup_from_cont(cont));
460 static int mem_cgroup_populate(struct cgroup_subsys *ss,
463 return cgroup_add_files(cont, ss, mem_cgroup_files,
464 ARRAY_SIZE(mem_cgroup_files));
467 static void mem_cgroup_move_task(struct cgroup_subsys *ss,
469 struct cgroup *old_cont,
470 struct task_struct *p)
472 struct mm_struct *mm;
473 struct mem_cgroup *mem, *old_mem;
479 mem = mem_cgroup_from_cont(cont);
480 old_mem = mem_cgroup_from_cont(old_cont);
486 * Only thread group leaders are allowed to migrate, the mm_struct is
487 * in effect owned by the leader
489 if (p->tgid != p->pid)
493 rcu_assign_pointer(mm->mem_cgroup, mem);
494 css_put(&old_mem->css);
501 struct cgroup_subsys mem_cgroup_subsys = {
503 .subsys_id = mem_cgroup_subsys_id,
504 .create = mem_cgroup_create,
505 .destroy = mem_cgroup_destroy,
506 .populate = mem_cgroup_populate,
507 .attach = mem_cgroup_move_task,