aboutsummaryrefslogtreecommitdiff
path: root/mm/memcontrol.c
blob: b25df2a9d024a5673cd573ef4fc8b0adc184f671 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
/* memcontrol.c - Memory Controller
 *
 * Copyright IBM Corporation, 2007
 * Author Balbir Singh <balbir@linux.vnet.ibm.com>
 *
 * Copyright 2007 OpenVZ SWsoft Inc
 * Author: Pavel Emelianov <xemul@openvz.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/res_counter.h>
#include <linux/memcontrol.h>
#include <linux/cgroup.h>
#include <linux/mm.h>
#include <linux/page-flags.h>
#include <linux/bit_spinlock.h>
#include <linux/rcupdate.h>

struct cgroup_subsys mem_cgroup_subsys;

/*
 * The memory controller data structure. The memory controller controls both
 * page cache and RSS per cgroup. We would eventually like to provide
 * statistics based on the statistics developed by Rik Van Riel for clock-pro,
 * to help the administrator determine what knobs to tune.
 *
 * TODO: Add a water mark for the memory controller. Reclaim will begin when
 * we hit the water mark. May be even add a low water mark, such that
 * no reclaim occurs from a cgroup at it's low water mark, this is
 * a feature that will be implemented much later in the future.
 */
struct mem_cgroup {
	struct cgroup_subsys_state css;
	/*
	 * the counter to account for memory usage
	 */
	struct res_counter res;
	/*
	 * Per cgroup active and inactive list, similar to the
	 * per zone LRU lists.
	 * TODO: Consider making these lists per zone
	 */
	struct list_head active_list;
	struct list_head inactive_list;
};

/*
 * We use the lower bit of the page->page_cgroup pointer as a bit spin
 * lock. We need to ensure that page->page_cgroup is atleast two
 * byte aligned (based on comments from Nick Piggin)
 */
#define PAGE_CGROUP_LOCK_BIT 	0x0
#define PAGE_CGROUP_LOCK 		(1 << PAGE_CGROUP_LOCK_BIT)

/*
 * A page_cgroup page is associated with every page descriptor. The
 * page_cgroup helps us identify information about the cgroup
 */
struct page_cgroup {
	struct list_head lru;		/* per cgroup LRU list */
	struct page *page;
	struct mem_cgroup *mem_cgroup;
	atomic_t ref_cnt;		/* Helpful when pages move b/w  */
					/* mapped and cached states     */
};


static inline
struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
{
	return container_of(cgroup_subsys_state(cont,
				mem_cgroup_subsys_id), struct mem_cgroup,
				css);
}

static inline
struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
{
	return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
				struct mem_cgroup, css);
}

void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p)
{
	struct mem_cgroup *mem;

	mem = mem_cgroup_from_task(p);
	css_get(&mem->css);
	mm->mem_cgroup = mem;
}

void mm_free_cgroup(struct mm_struct *mm)
{
	css_put(&mm->mem_cgroup->css);
}

static inline int page_cgroup_locked(struct page *page)
{
	return bit_spin_is_locked(PAGE_CGROUP_LOCK_BIT,
					&page->page_cgroup);
}

void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
{
	int locked;

	/*
	 * While resetting the page_cgroup we might not hold the
	 * page_cgroup lock. free_hot_cold_page() is an example
	 * of such a scenario
	 */
	if (pc)
		VM_BUG_ON(!page_cgroup_locked(page));
	locked = (page->page_cgroup & PAGE_CGROUP_LOCK);
	page->page_cgroup = ((unsigned long)pc | locked);
}

struct page_cgroup *page_get_page_cgroup(struct page *page)
{
	return (struct page_cgroup *)
		(page->page_cgroup & ~PAGE_CGROUP_LOCK);
}

void __always_inline lock_page_cgroup(struct page *page)
{
	bit_spin_lock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
	VM_BUG_ON(!page_cgroup_locked(page));
}

void __always_inline unlock_page_cgroup(struct page *page)
{
	bit_spin_unlock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
}

/*
 * Charge the memory controller for page usage.
 * Return
 * 0 if the charge was successful
 * < 0 if the cgroup is over its limit
 */
int mem_cgroup_charge(struct page *page, struct mm_struct *mm)
{
	struct mem_cgroup *mem;
	struct page_cgroup *pc, *race_pc;

	/*
	 * Should page_cgroup's go to their own slab?
	 * One could optimize the performance of the charging routine
	 * by saving a bit in the page_flags and using it as a lock
	 * to see if the cgroup page already has a page_cgroup associated
	 * with it
	 */
	lock_page_cgroup(page);
	pc = page_get_page_cgroup(page);
	/*
	 * The page_cgroup exists and the page has already been accounted
	 */
	if (pc) {
		atomic_inc(&pc->ref_cnt);
		goto done;
	}

	unlock_page_cgroup(page);

	pc = kzalloc(sizeof(struct page_cgroup), GFP_KERNEL);
	if (pc == NULL)
		goto err;

	rcu_read_lock();
	/*
	 * We always charge the cgroup the mm_struct belongs to
	 * the mm_struct's mem_cgroup changes on task migration if the
	 * 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;

	mem = rcu_dereference(mm->mem_cgroup);
	/*
	 * For every charge from the cgroup, increment reference
	 * count
	 */
	css_get(&mem->css);
	rcu_read_unlock();

	/*
	 * If we created the page_cgroup, we should free it on exceeding
	 * the cgroup limit.
	 */
	if (res_counter_charge(&mem->res, 1)) {
		css_put(&mem->css);
		goto free_pc;
	}

	lock_page_cgroup(page);
	/*
	 * Check if somebody else beat us to allocating the page_cgroup
	 */
	race_pc = page_get_page_cgroup(page);
	if (race_pc) {
		kfree(pc);
		pc = race_pc;
		atomic_inc(&pc->ref_cnt);
		res_counter_uncharge(&mem->res, 1);
		css_put(&mem->css);
		goto done;
	}

	atomic_set(&pc->ref_cnt, 1);
	pc->mem_cgroup = mem;
	pc->page = page;
	page_assign_page_cgroup(page, pc);

done:
	unlock_page_cgroup(page);
	return 0;
free_pc:
	kfree(pc);
	return -ENOMEM;
err:
	unlock_page_cgroup(page);
	return -ENOMEM;
}

/*
 * Uncharging is always a welcome operation, we never complain, simply
 * uncharge.
 */
void mem_cgroup_uncharge(struct page_cgroup *pc)
{
	struct mem_cgroup *mem;
	struct page *page;

	if (!pc)
		return;

	if (atomic_dec_and_test(&pc->ref_cnt)) {
		page = pc->page;
		lock_page_cgroup(page);
		mem = pc->mem_cgroup;
		css_put(&mem->css);
		page_assign_page_cgroup(page, NULL);
		unlock_page_cgroup(page);
		res_counter_uncharge(&mem->res, 1);
		kfree(pc);
	}
}

static ssize_t mem_cgroup_read(struct cgroup *cont, struct cftype *cft,
			struct file *file, char __user *userbuf, size_t nbytes,
			loff_t *ppos)
{
	return res_counter_read(&mem_cgroup_from_cont(cont)->res,
				cft->private, userbuf, nbytes, ppos);
}

static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
				struct file *file, const char __user *userbuf,
				size_t nbytes, loff_t *ppos)
{
	return res_counter_write(&mem_cgroup_from_cont(cont)->res,
				cft->private, userbuf, nbytes, ppos);
}

static struct cftype mem_cgroup_files[] = {
	{
		.name = "usage",
		.private = RES_USAGE,
		.read = mem_cgroup_read,
	},
	{
		.name = "limit",
		.private = RES_LIMIT,
		.write = mem_cgroup_write,
		.read = mem_cgroup_read,
	},
	{
		.name = "failcnt",
		.private = RES_FAILCNT,
		.read = mem_cgroup_read,
	},
};

static struct mem_cgroup init_mem_cgroup;

static struct cgroup_subsys_state *
mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
{
	struct mem_cgroup *mem;

	if (unlikely((cont->parent) == NULL)) {
		mem = &init_mem_cgroup;
		init_mm.mem_cgroup = mem;
	} else
		mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);

	if (mem == NULL)
		return NULL;

	res_counter_init(&mem->res);
	INIT_LIST_HEAD(&mem->active_list);
	INIT_LIST_HEAD(&mem->inactive_list);
	return &mem->css;
}

static void mem_cgroup_destroy(struct cgroup_subsys *ss,
				struct cgroup *cont)
{
	kfree(mem_cgroup_from_cont(cont));
}

static int mem_cgroup_populate(struct cgroup_subsys *ss,
				struct cgroup *cont)
{
	return cgroup_add_files(cont, ss, mem_cgroup_files,
					ARRAY_SIZE(mem_cgroup_files));
}

static void mem_cgroup_move_task(struct cgroup_subsys *ss,
				struct cgroup *cont,
				struct cgroup *old_cont,
				struct task_struct *p)
{
	struct mm_struct *mm;
	struct mem_cgroup *mem, *old_mem;

	mm = get_task_mm(p);
	if (mm == NULL)
		return;

	mem = mem_cgroup_from_cont(cont);
	old_mem = mem_cgroup_from_cont(old_cont);

	if (mem == old_mem)
		goto out;

	/*
	 * Only thread group leaders are allowed to migrate, the mm_struct is
	 * in effect owned by the leader
	 */
	if (p->tgid != p->pid)
		goto out;

	css_get(&mem->css);
	rcu_assign_pointer(mm->mem_cgroup, mem);
	css_put(&old_mem->css);

out:
	mmput(mm);
	return;
}

struct cgroup_subsys mem_cgroup_subsys = {
	.name = "memory",
	.subsys_id = mem_cgroup_subsys_id,
	.create = mem_cgroup_create,
	.destroy = mem_cgroup_destroy,
	.populate = mem_cgroup_populate,
	.attach = mem_cgroup_move_task,
	.early_init = 1,
};