mm: memcontrol: lockless page counters

Memory is internally accounted in bytes, using spinlock-protected 64-bit
counters, even though the smallest accounting delta is a page. The
counter interface is also convoluted and does too many things.

Introduce a new lockless word-sized page counter API, then change all
memory accounting over to it. The translation from and to bytes then only
happens when interfacing with userspace.

The removed locking overhead is noticable when scaling beyond the per-cpu
charge caches - on a 4-socket machine with 144-threads, the following test
shows the performance differences of 288 memcgs concurrently running a
page fault benchmark:

vanilla:

18631648.500498 task-clock (msec) # 140.643 CPUs utilized ( +- 0.33% )
1,380,638 context-switches # 0.074 K/sec ( +- 0.75% )
24,390 cpu-migrations # 0.001 K/sec ( +- 8.44% )
1,843,305,768 page-faults # 0.099 M/sec ( +- 0.00% )
50,134,994,088,218 cycles # 2.691 GHz ( +- 0.33% )
<not supported> stalled-cycles-frontend
<not supported> stalled-cycles-backend
8,049,712,224,651 instructions # 0.16 insns per cycle ( +- 0.04% )
1,586,970,584,979 branches # 85.176 M/sec ( +- 0.05% )
1,724,989,949 branch-misses # 0.11% of all branches ( +- 0.48% )

132.474343877 seconds time elapsed ( +- 0.21% )

lockless:

12195979.037525 task-clock (msec) # 133.480 CPUs utilized ( +- 0.18% )
832,850 context-switches # 0.068 K/sec ( +- 0.54% )
15,624 cpu-migrations # 0.001 K/sec ( +- 10.17% )
1,843,304,774 page-faults # 0.151 M/sec ( +- 0.00% )
32,811,216,801,141 cycles # 2.690 GHz ( +- 0.18% )
<not supported> stalled-cycles-frontend
<not supported> stalled-cycles-backend
9,999,265,091,727 instructions # 0.30 insns per cycle ( +- 0.10% )
2,076,759,325,203 branches # 170.282 M/sec ( +- 0.12% )
1,656,917,214 branch-misses # 0.08% of all branches ( +- 0.55% )

91.369330729 seconds time elapsed ( +- 0.45% )

On top of improved scalability, this also gets rid of the icky long long
types in the very heart of memcg, which is great for 32 bit and also makes
the code a lot more readable.

Notable differences between the old and new API:

- res_counter_charge() and res_counter_charge_nofail() become
page_counter_try_charge() and page_counter_charge() resp. to match
the more common kernel naming scheme of try_do()/do()

- res_counter_uncharge_until() is only ever used to cancel a local
counter and never to uncharge bigger segments of a hierarchy, so
it's replaced by the simpler page_counter_cancel()

- res_counter_set_limit() is replaced by page_counter_limit(), which
expects its callers to serialize against themselves

- res_counter_memparse_write_strategy() is replaced by
page_counter_limit(), which rounds down to the nearest page size -
rather than up. This is more reasonable for explicitely requested
hard upper limits.

- to keep charging light-weight, page_counter_try_charge() charges
speculatively, only to roll back if the result exceeds the limit.
Because of this, a failing bigger charge can temporarily lock out
smaller charges that would otherwise succeed. The error is bounded
to the difference between the smallest and the biggest possible
charge size, so for memcg, this means that a failing THP charge can
send base page charges into reclaim upto 2MB (4MB) before the limit
would have been reached. This should be acceptable.

[[e-mail]: add includes for WARN_ON_ONCE and memparse]
[[e-mail]: add includes for WARN_ON_ONCE, memparse, strncmp, and PAGE_SIZE]
Signed-off-by: Johannes Weiner <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Acked-by: Vladimir Davydov <[e-mail]>
Cc: Tejun Heo <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/cgroups/memory.txt

···
  tasks				 # attach a task(thread) and show list of threads
  cgroup.procs			 # show list of processes
  cgroup.event_control		 # an interface for event_fd()
- memory.usage_in_bytes		 # show current res_counter usage for memory
+ memory.usage_in_bytes		 # show current usage for memory
 				 (See 5.5 for details)
- memory.memsw.usage_in_bytes	 # show current res_counter usage for memory+Swap
+ memory.memsw.usage_in_bytes	 # show current usage for memory+Swap
 				 (See 5.5 for details)
  memory.limit_in_bytes		 # set/show limit of memory usage
  memory.memsw.limit_in_bytes	 # set/show limit of memory+Swap usage

include/linux/memcontrol.h

···
 	/*
 	 * __GFP_NOFAIL allocations will move on even if charging is not
 	 * possible. Therefore we don't even try, and have this allocation
-	 * unaccounted. We could in theory charge it with
-	 * res_counter_charge_nofail, but we hope those allocations are rare,
-	 * and won't be worth the trouble.
+	 * unaccounted. We could in theory charge it forcibly, but we hope
+	 * those allocations are rare, and won't be worth the trouble.
 	 */
 	if (gfp & __GFP_NOFAIL)
 		return true;

include/linux/page_counter.h

···
+#ifndef _LINUX_PAGE_COUNTER_H
+#define _LINUX_PAGE_COUNTER_H
+
+#include <linux/atomic.h>
+#include <linux/kernel.h>
+#include <asm/page.h>
+
+struct page_counter {
+	atomic_long_t count;
+	unsigned long limit;
+	struct page_counter *parent;
+
+	/* legacy */
+	unsigned long watermark;
+	unsigned long failcnt;
+};
+
+#if BITS_PER_LONG == 32
+#define PAGE_COUNTER_MAX LONG_MAX
+#else
+#define PAGE_COUNTER_MAX (LONG_MAX / PAGE_SIZE)
+#endif
+
+static inline void page_counter_init(struct page_counter *counter,
+				     struct page_counter *parent)
+{
+	atomic_long_set(&counter->count, 0);
+	counter->limit = PAGE_COUNTER_MAX;
+	counter->parent = parent;
+}
+
+static inline unsigned long page_counter_read(struct page_counter *counter)
+{
+	return atomic_long_read(&counter->count);
+}
+
+int page_counter_cancel(struct page_counter *counter, unsigned long nr_pages);
+void page_counter_charge(struct page_counter *counter, unsigned long nr_pages);
+int page_counter_try_charge(struct page_counter *counter,
+			    unsigned long nr_pages,
+			    struct page_counter **fail);
+int page_counter_uncharge(struct page_counter *counter, unsigned long nr_pages);
+int page_counter_limit(struct page_counter *counter, unsigned long limit);
+int page_counter_memparse(const char *buf, unsigned long *nr_pages);
+
+static inline void page_counter_reset_watermark(struct page_counter *counter)
+{
+	counter->watermark = page_counter_read(counter);
+}
+
+#endif /* _LINUX_PAGE_COUNTER_H */

include/net/sock.h

···
 #include <linux/security.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
+#include <linux/page_counter.h>
 #include <linux/memcontrol.h>
-#include <linux/res_counter.h>
 #include <linux/static_key.h>
 #include <linux/aio.h>
 #include <linux/sched.h>
···
 };
 
 struct cg_proto {
-	struct res_counter	memory_allocated;	/* Current allocated memory. */
+	struct page_counter	memory_allocated;	/* Current allocated memory. */
 	struct percpu_counter	sockets_allocated;	/* Current number of sockets. */
 	int			memory_pressure;
 	long			sysctl_mem[3];
···
 					      unsigned long amt,
 					      int *parent_status)
 {
-	struct res_counter *fail;
-	int ret;
+	page_counter_charge(&prot->memory_allocated, amt);
 
-	ret = res_counter_charge_nofail(&prot->memory_allocated,
-					amt << PAGE_SHIFT, &fail);
-	if (ret < 0)
+	if (page_counter_read(&prot->memory_allocated) >
+	    prot->memory_allocated.limit)
 		*parent_status = OVER_LIMIT;
 }
 
 static inline void memcg_memory_allocated_sub(struct cg_proto *prot,
 					      unsigned long amt)
 {
-	res_counter_uncharge(&prot->memory_allocated, amt << PAGE_SHIFT);
-}
-
-static inline u64 memcg_memory_allocated_read(struct cg_proto *prot)
-{
-	u64 ret;
-	ret = res_counter_read_u64(&prot->memory_allocated, RES_USAGE);
-	return ret >> PAGE_SHIFT;
+	page_counter_uncharge(&prot->memory_allocated, amt);
 }
 
 static inline long
 sk_memory_allocated(const struct sock *sk)
 {
 	struct proto *prot = sk->sk_prot;
+
 	if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
-		return memcg_memory_allocated_read(sk->sk_cgrp);
+		return page_counter_read(&sk->sk_cgrp->memory_allocated);
 
 	return atomic_long_read(prot->memory_allocated);
 }
···
 		memcg_memory_allocated_add(sk->sk_cgrp, amt, parent_status);
 		/* update the root cgroup regardless */
 		atomic_long_add_return(amt, prot->memory_allocated);
-		return memcg_memory_allocated_read(sk->sk_cgrp);
+		return page_counter_read(&sk->sk_cgrp->memory_allocated);
 	}
 
 	return atomic_long_add_return(amt, prot->memory_allocated);

init/Kconfig

···
 	  This option enables controller independent resource accounting
 	  infrastructure that works with cgroups.
 
+config PAGE_COUNTER
+       bool
+
 config MEMCG
 	bool "Memory Resource Controller for Control Groups"
-	depends on RESOURCE_COUNTERS
+	select PAGE_COUNTER
 	select EVENTFD
 	help
 	  Provides a memory resource controller that manages both anonymous

mm/Makefile

···
 obj-$(CONFIG_MIGRATION) += migrate.o
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o
+obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
 obj-$(CONFIG_MEMCG) += memcontrol.o page_cgroup.o vmpressure.o
 obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o
 obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o

mm/memcontrol.c

···
  * GNU General Public License for more details.
  */
 
-#include <linux/res_counter.h>
+#include <linux/page_counter.h>
 #include <linux/memcontrol.h>
 #include <linux/cgroup.h>
 #include <linux/mm.h>
···
 	struct mem_cgroup_reclaim_iter reclaim_iter[DEF_PRIORITY + 1];
 
 	struct rb_node		tree_node;	/* RB tree node */
-	unsigned long long	usage_in_excess;/* Set to the value by which */
+	unsigned long		usage_in_excess;/* Set to the value by which */
 						/* the soft limit is exceeded*/
 	bool			on_tree;
 	struct mem_cgroup	*memcg;		/* Back pointer, we cannot */
···
 
 struct mem_cgroup_threshold {
 	struct eventfd_ctx *eventfd;
-	u64 threshold;
+	unsigned long threshold;
 };
 
 /* For threshold */
···
  */
 struct mem_cgroup {
 	struct cgroup_subsys_state css;
-	/*
-	 * the counter to account for memory usage
-	 */
-	struct res_counter res;
+
+	/* Accounted resources */
+	struct page_counter memory;
+	struct page_counter memsw;
+	struct page_counter kmem;
+
+	unsigned long soft_limit;
 
 	/* vmpressure notifications */
 	struct vmpressure vmpressure;
···
 	/* css_online() has been completed */
 	int initialized;
 
-	/*
-	 * the counter to account for mem+swap usage.
-	 */
-	struct res_counter memsw;
-
-	/*
-	 * the counter to account for kernel memory usage.
-	 */
-	struct res_counter kmem;
 	/*
 	 * Should the accounting and control be hierarchical, per subtree?
 	 */
···
 	 * This check can't live in kmem destruction function,
 	 * since the charges will outlive the cgroup
 	 */
-	WARN_ON(res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0);
+	WARN_ON(page_counter_read(&memcg->kmem));
 }
 #else
 static void disarm_kmem_keys(struct mem_cgroup *memcg)
···
 
 static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_zone *mz,
 					 struct mem_cgroup_tree_per_zone *mctz,
-					 unsigned long long new_usage_in_excess)
+					 unsigned long new_usage_in_excess)
 {
 	struct rb_node **p = &mctz->rb_root.rb_node;
 	struct rb_node *parent = NULL;
···
 	spin_unlock_irqrestore(&mctz->lock, flags);
 }
 
+static unsigned long soft_limit_excess(struct mem_cgroup *memcg)
+{
+	unsigned long nr_pages = page_counter_read(&memcg->memory);
+	unsigned long soft_limit = ACCESS_ONCE(memcg->soft_limit);
+	unsigned long excess = 0;
+
+	if (nr_pages > soft_limit)
+		excess = nr_pages - soft_limit;
+
+	return excess;
+}
 
 static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
 {
-	unsigned long long excess;
+	unsigned long excess;
 	struct mem_cgroup_per_zone *mz;
 	struct mem_cgroup_tree_per_zone *mctz;
 
···
 	 */
 	for (; memcg; memcg = parent_mem_cgroup(memcg)) {
 		mz = mem_cgroup_page_zoneinfo(memcg, page);
-		excess = res_counter_soft_limit_excess(&memcg->res);
+		excess = soft_limit_excess(memcg);
 		/*
 		 * We have to update the tree if mz is on RB-tree or
 		 * mem is over its softlimit.
···
 	 * position in the tree.
 	 */
 	__mem_cgroup_remove_exceeded(mz, mctz);
-	if (!res_counter_soft_limit_excess(&mz->memcg->res) ||
+	if (!soft_limit_excess(mz->memcg) ||
 	    !css_tryget_online(&mz->memcg->css))
 		goto retry;
 done:
···
 	return inactive * inactive_ratio < active;
 }
 
-#define mem_cgroup_from_res_counter(counter, member)	\
+#define mem_cgroup_from_counter(counter, member)	\
 	container_of(counter, struct mem_cgroup, member)
 
 /**
···
  */
 static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
 {
-	unsigned long long margin;
+	unsigned long margin = 0;
+	unsigned long count;
+	unsigned long limit;
 
-	margin = res_counter_margin(&memcg->res);
-	if (do_swap_account)
-		margin = min(margin, res_counter_margin(&memcg->memsw));
-	return margin >> PAGE_SHIFT;
+	count = page_counter_read(&memcg->memory);
+	limit = ACCESS_ONCE(memcg->memory.limit);
+	if (count < limit)
+		margin = limit - count;
+
+	if (do_swap_account) {
+		count = page_counter_read(&memcg->memsw);
+		limit = ACCESS_ONCE(memcg->memsw.limit);
+		if (count <= limit)
+			margin = min(margin, limit - count);
+	}
+
+	return margin;
 }
 
 int mem_cgroup_swappiness(struct mem_cgroup *memcg)
···
 
 	rcu_read_unlock();
 
-	pr_info("memory: usage %llukB, limit %llukB, failcnt %llu\n",
-		res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
-		res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
-		res_counter_read_u64(&memcg->res, RES_FAILCNT));
-	pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %llu\n",
-		res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
-		res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
-		res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
-	pr_info("kmem: usage %llukB, limit %llukB, failcnt %llu\n",
-		res_counter_read_u64(&memcg->kmem, RES_USAGE) >> 10,
-		res_counter_read_u64(&memcg->kmem, RES_LIMIT) >> 10,
-		res_counter_read_u64(&memcg->kmem, RES_FAILCNT));
+	pr_info("memory: usage %llukB, limit %llukB, failcnt %lu\n",
+		K((u64)page_counter_read(&memcg->memory)),
+		K((u64)memcg->memory.limit), memcg->memory.failcnt);
+	pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %lu\n",
+		K((u64)page_counter_read(&memcg->memsw)),
+		K((u64)memcg->memsw.limit), memcg->memsw.failcnt);
+	pr_info("kmem: usage %llukB, limit %llukB, failcnt %lu\n",
+		K((u64)page_counter_read(&memcg->kmem)),
+		K((u64)memcg->kmem.limit), memcg->kmem.failcnt);
 
 	for_each_mem_cgroup_tree(iter, memcg) {
 		pr_info("Memory cgroup stats for ");
···
 /*
  * Return the memory (and swap, if configured) limit for a memcg.
  */
-static u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
+static unsigned long mem_cgroup_get_limit(struct mem_cgroup *memcg)
 {
-	u64 limit;
+	unsigned long limit;
 
-	limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
-
-	/*
-	 * Do not consider swap space if we cannot swap due to swappiness
-	 */
+	limit = memcg->memory.limit;
 	if (mem_cgroup_swappiness(memcg)) {
-		u64 memsw;
+		unsigned long memsw_limit;
 
-		limit += total_swap_pages << PAGE_SHIFT;
-		memsw = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
-
-		/*
-		 * If memsw is finite and limits the amount of swap space
-		 * available to this memcg, return that limit.
-		 */
-		limit = min(limit, memsw);
+		memsw_limit = memcg->memsw.limit;
+		limit = min(limit + total_swap_pages, memsw_limit);
 	}
-
 	return limit;
 }
 
···
 	}
 
 	check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, order, NULL);
-	totalpages = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT ? : 1;
+	totalpages = mem_cgroup_get_limit(memcg) ? : 1;
 	for_each_mem_cgroup_tree(iter, memcg) {
 		struct css_task_iter it;
 		struct task_struct *task;
···
 		.priority = 0,
 	};
 
-	excess = res_counter_soft_limit_excess(&root_memcg->res) >> PAGE_SHIFT;
+	excess = soft_limit_excess(root_memcg);
 
 	while (1) {
 		victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
···
 		total += mem_cgroup_shrink_node_zone(victim, gfp_mask, false,
 						     zone, &nr_scanned);
 		*total_scanned += nr_scanned;
-		if (!res_counter_soft_limit_excess(&root_memcg->res))
+		if (!soft_limit_excess(root_memcg))
 			break;
 	}
 	mem_cgroup_iter_break(root_memcg, victim);
···
 static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
 	struct memcg_stock_pcp *stock;
-	bool ret = true;
+	bool ret = false;
 
 	if (nr_pages > CHARGE_BATCH)
-		return false;
+		return ret;
 
 	stock = &get_cpu_var(memcg_stock);
-	if (memcg == stock->cached && stock->nr_pages >= nr_pages)
+	if (memcg == stock->cached && stock->nr_pages >= nr_pages) {
 		stock->nr_pages -= nr_pages;
-	else /* need to call res_counter_charge */
-		ret = false;
+		ret = true;
+	}
 	put_cpu_var(memcg_stock);
 	return ret;
 }
 
 /*
- * Returns stocks cached in percpu to res_counter and reset cached information.
+ * Returns stocks cached in percpu and reset cached information.
  */
 static void drain_stock(struct memcg_stock_pcp *stock)
 {
 	struct mem_cgroup *old = stock->cached;
 
 	if (stock->nr_pages) {
-		unsigned long bytes = stock->nr_pages * PAGE_SIZE;
-
-		res_counter_uncharge(&old->res, bytes);
+		page_counter_uncharge(&old->memory, stock->nr_pages);
 		if (do_swap_account)
-			res_counter_uncharge(&old->memsw, bytes);
+			page_counter_uncharge(&old->memsw, stock->nr_pages);
 		stock->nr_pages = 0;
 	}
 	stock->cached = NULL;
···
 }
 
 /*
- * Cache charges(val) which is from res_counter, to local per_cpu area.
+ * Cache charges(val) to local per_cpu area.
  * This will be consumed by consume_stock() function, later.
  */
 static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
···
 /*
  * Tries to drain stocked charges in other cpus. This function is asynchronous
  * and just put a work per cpu for draining localy on each cpu. Caller can
- * expects some charges will be back to res_counter later but cannot wait for
- * it.
+ * expects some charges will be back later but cannot wait for it.
  */
 static void drain_all_stock_async(struct mem_cgroup *root_memcg)
 {
···
 	unsigned int batch = max(CHARGE_BATCH, nr_pages);
 	int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
 	struct mem_cgroup *mem_over_limit;
-	struct res_counter *fail_res;
+	struct page_counter *counter;
 	unsigned long nr_reclaimed;
-	unsigned long long size;
 	bool may_swap = true;
 	bool drained = false;
 	int ret = 0;
···
 	if (consume_stock(memcg, nr_pages))
 		goto done;
 
-	size = batch * PAGE_SIZE;
 	if (!do_swap_account ||
-	    !res_counter_charge(&memcg->memsw, size, &fail_res)) {
-		if (!res_counter_charge(&memcg->res, size, &fail_res))
+	    !page_counter_try_charge(&memcg->memsw, batch, &counter)) {
+		if (!page_counter_try_charge(&memcg->memory, batch, &counter))
 			goto done_restock;
 		if (do_swap_account)
-			res_counter_uncharge(&memcg->memsw, size);
-		mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
+			page_counter_uncharge(&memcg->memsw, batch);
+		mem_over_limit = mem_cgroup_from_counter(counter, memory);
 	} else {
-		mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw);
+		mem_over_limit = mem_cgroup_from_counter(counter, memsw);
 		may_swap = false;
 	}
 
···
 
 static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
-	unsigned long bytes = nr_pages * PAGE_SIZE;
-
 	if (mem_cgroup_is_root(memcg))
 		return;
 
-	res_counter_uncharge(&memcg->res, bytes);
+	page_counter_uncharge(&memcg->memory, nr_pages);
 	if (do_swap_account)
-		res_counter_uncharge(&memcg->memsw, bytes);
-}
-
-/*
- * Cancel chrages in this cgroup....doesn't propagate to parent cgroup.
- * This is useful when moving usage to parent cgroup.
- */
-static void __mem_cgroup_cancel_local_charge(struct mem_cgroup *memcg,
-					unsigned int nr_pages)
-{
-	unsigned long bytes = nr_pages * PAGE_SIZE;
-
-	if (mem_cgroup_is_root(memcg))
-		return;
-
-	res_counter_uncharge_until(&memcg->res, memcg->res.parent, bytes);
-	if (do_swap_account)
-		res_counter_uncharge_until(&memcg->memsw,
-						memcg->memsw.parent, bytes);
+		page_counter_uncharge(&memcg->memsw, nr_pages);
 }
 
 /*
···
 		unlock_page_lru(page, isolated);
 }
 
-static DEFINE_MUTEX(set_limit_mutex);
-
 #ifdef CONFIG_MEMCG_KMEM
 /*
  * The memcg_slab_mutex is held whenever a per memcg kmem cache is created or
···
 }
 #endif
 
-static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
+static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp,
+			     unsigned long nr_pages)
 {
-	struct res_counter *fail_res;
+	struct page_counter *counter;
 	int ret = 0;
 
-	ret = res_counter_charge(&memcg->kmem, size, &fail_res);
-	if (ret)
+	ret = page_counter_try_charge(&memcg->kmem, nr_pages, &counter);
+	if (ret < 0)
 		return ret;
 
-	ret = try_charge(memcg, gfp, size >> PAGE_SHIFT);
+	ret = try_charge(memcg, gfp, nr_pages);
 	if (ret == -EINTR)  {
 		/*
 		 * try_charge() chose to bypass to root due to OOM kill or
···
 		 * when the allocation triggers should have been already
 		 * directed to the root cgroup in memcontrol.h
 		 */
-		res_counter_charge_nofail(&memcg->res, size, &fail_res);
+		page_counter_charge(&memcg->memory, nr_pages);
 		if (do_swap_account)
-			res_counter_charge_nofail(&memcg->memsw, size,
-						  &fail_res);
+			page_counter_charge(&memcg->memsw, nr_pages);
 		ret = 0;
 	} else if (ret)
-		res_counter_uncharge(&memcg->kmem, size);
+		page_counter_uncharge(&memcg->kmem, nr_pages);
 
 	return ret;
 }
 
-static void memcg_uncharge_kmem(struct mem_cgroup *memcg, u64 size)
+static void memcg_uncharge_kmem(struct mem_cgroup *memcg,
+				unsigned long nr_pages)
 {
-	res_counter_uncharge(&memcg->res, size);
+	page_counter_uncharge(&memcg->memory, nr_pages);
 	if (do_swap_account)
-		res_counter_uncharge(&memcg->memsw, size);
+		page_counter_uncharge(&memcg->memsw, nr_pages);
 
 	/* Not down to 0 */
-	if (res_counter_uncharge(&memcg->kmem, size))
+	if (page_counter_uncharge(&memcg->kmem, nr_pages))
 		return;
 
 	/*
···
 
 int __memcg_charge_slab(struct kmem_cache *cachep, gfp_t gfp, int order)
 {
+	unsigned int nr_pages = 1 << order;
 	int res;
 
-	res = memcg_charge_kmem(cachep->memcg_params->memcg, gfp,
-				PAGE_SIZE << order);
+	res = memcg_charge_kmem(cachep->memcg_params->memcg, gfp, nr_pages);
 	if (!res)
-		atomic_add(1 << order, &cachep->memcg_params->nr_pages);
+		atomic_add(nr_pages, &cachep->memcg_params->nr_pages);
 	return res;
 }
 
 void __memcg_uncharge_slab(struct kmem_cache *cachep, int order)
 {
-	memcg_uncharge_kmem(cachep->memcg_params->memcg, PAGE_SIZE << order);
-	atomic_sub(1 << order, &cachep->memcg_params->nr_pages);
+	unsigned int nr_pages = 1 << order;
+
+	memcg_uncharge_kmem(cachep->memcg_params->memcg, nr_pages);
+	atomic_sub(nr_pages, &cachep->memcg_params->nr_pages);
 }
 
 /*
···
 		return true;
 	}
 
-	ret = memcg_charge_kmem(memcg, gfp, PAGE_SIZE << order);
+	ret = memcg_charge_kmem(memcg, gfp, 1 << order);
 	if (!ret)
 		*_memcg = memcg;
 
···
 
 	/* The page allocation failed. Revert */
 	if (!page) {
-		memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
+		memcg_uncharge_kmem(memcg, 1 << order);
 		return;
 	}
 	/*
···
 		return;
 
 	VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page);
-	memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
+	memcg_uncharge_kmem(memcg, 1 << order);
 }
 #else
 static inline void memcg_unregister_all_caches(struct mem_cgroup *memcg)
···
 
 	ret = mem_cgroup_move_account(page, nr_pages,
 				pc, child, parent);
-	if (!ret)
-		__mem_cgroup_cancel_local_charge(child, nr_pages);
+	if (!ret) {
+		/* Take charge off the local counters */
+		page_counter_cancel(&child->memory, nr_pages);
+		if (do_swap_account)
+			page_counter_cancel(&child->memsw, nr_pages);
+	}
 
 	if (nr_pages > 1)
 		compound_unlock_irqrestore(page, flags);
···
  *
  * Returns 0 on success, -EINVAL on failure.
  *
- * The caller must have charged to @to, IOW, called res_counter_charge() about
+ * The caller must have charged to @to, IOW, called page_counter_charge() about
  * both res and memsw, and called css_get().
  */
 static int mem_cgroup_move_swap_account(swp_entry_t entry,
···
 		mem_cgroup_swap_statistics(to, true);
 		/*
 		 * This function is only called from task migration context now.
-		 * It postpones res_counter and refcount handling till the end
+		 * It postpones page_counter and refcount handling till the end
 		 * of task migration(mem_cgroup_clear_mc()) for performance
 		 * improvement. But we cannot postpone css_get(to)  because if
 		 * the process that has been moved to @to does swap-in, the
···
 }
 #endif
 
+static DEFINE_MUTEX(memcg_limit_mutex);
+
 static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
-				unsigned long long val)
+				   unsigned long limit)
 {
+	unsigned long curusage;
+	unsigned long oldusage;
+	bool enlarge = false;
 	int retry_count;
-	int ret = 0;
-	int children = mem_cgroup_count_children(memcg);
-	u64 curusage, oldusage;
-	int enlarge;
+	int ret;
 
 	/*
 	 * For keeping hierarchical_reclaim simple, how long we should retry
 	 * is depends on callers. We set our retry-count to be function
 	 * of # of children which we should visit in this loop.
 	 */
-	retry_count = MEM_CGROUP_RECLAIM_RETRIES * children;
+	retry_count = MEM_CGROUP_RECLAIM_RETRIES *
+		      mem_cgroup_count_children(memcg);
 
-	oldusage = res_counter_read_u64(&memcg->res, RES_USAGE);
+	oldusage = page_counter_read(&memcg->memory);
 
-	enlarge = 0;
-	while (retry_count) {
+	do {
 		if (signal_pending(current)) {
 			ret = -EINTR;
 			break;
 		}
-		/*
-		 * Rather than hide all in some function, I do this in
-		 * open coded manner. You see what this really does.
-		 * We have to guarantee memcg->res.limit <= memcg->memsw.limit.
-		 */
-		mutex_lock(&set_limit_mutex);
-		if (res_counter_read_u64(&memcg->memsw, RES_LIMIT) < val) {
+
+		mutex_lock(&memcg_limit_mutex);
+		if (limit > memcg->memsw.limit) {
+			mutex_unlock(&memcg_limit_mutex);
 			ret = -EINVAL;
-			mutex_unlock(&set_limit_mutex);
 			break;
 		}
-
-		if (res_counter_read_u64(&memcg->res, RES_LIMIT) < val)
-			enlarge = 1;
-
-		ret = res_counter_set_limit(&memcg->res, val);
-		mutex_unlock(&set_limit_mutex);
+		if (limit > memcg->memory.limit)
+			enlarge = true;
+		ret = page_counter_limit(&memcg->memory, limit);
+		mutex_unlock(&memcg_limit_mutex);
 
 		if (!ret)
 			break;
 
 		try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, true);
 
-		curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
+		curusage = page_counter_read(&memcg->memory);
 		/* Usage is reduced ? */
 		if (curusage >= oldusage)
 			retry_count--;
 		else
 			oldusage = curusage;
-	}
+	} while (retry_count);
+
 	if (!ret && enlarge)
 		memcg_oom_recover(memcg);
 
···
 }
 
 static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
-					unsigned long long val)
+					 unsigned long limit)
 {
+	unsigned long curusage;
+	unsigned long oldusage;
+	bool enlarge = false;
 	int retry_count;
-	u64 oldusage, curusage;
-	int children = mem_cgroup_count_children(memcg);
-	int ret = -EBUSY;
-	int enlarge = 0;
+	int ret;
 
 	/* see mem_cgroup_resize_res_limit */
-	retry_count = children * MEM_CGROUP_RECLAIM_RETRIES;
-	oldusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
-	while (retry_count) {
+	retry_count = MEM_CGROUP_RECLAIM_RETRIES *
+		      mem_cgroup_count_children(memcg);
+
+	oldusage = page_counter_read(&memcg->memsw);
+
+	do {
 		if (signal_pending(current)) {
 			ret = -EINTR;
 			break;
 		}
-		/*
-		 * Rather than hide all in some function, I do this in
-		 * open coded manner. You see what this really does.
-		 * We have to guarantee memcg->res.limit <= memcg->memsw.limit.
-		 */
-		mutex_lock(&set_limit_mutex);
-		if (res_counter_read_u64(&memcg->res, RES_LIMIT) > val) {
+
+		mutex_lock(&memcg_limit_mutex);
+		if (limit < memcg->memory.limit) {
+			mutex_unlock(&memcg_limit_mutex);
 			ret = -EINVAL;
-			mutex_unlock(&set_limit_mutex);
 			break;
 		}
-		if (res_counter_read_u64(&memcg->memsw, RES_LIMIT) < val)
-			enlarge = 1;
-		ret = res_counter_set_limit(&memcg->memsw, val);
-		mutex_unlock(&set_limit_mutex);
+		if (limit > memcg->memsw.limit)
+			enlarge = true;
+		ret = page_counter_limit(&memcg->memsw, limit);
+		mutex_unlock(&memcg_limit_mutex);
 
 		if (!ret)
 			break;
 
 		try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, false);
 
-		curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
+		curusage = page_counter_read(&memcg->memsw);
 		/* Usage is reduced ? */
 		if (curusage >= oldusage)
 			retry_count--;
 		else
 			oldusage = curusage;
-	}
+	} while (retry_count);
+
 	if (!ret && enlarge)
 		memcg_oom_recover(memcg);
+
 	return ret;
 }
 
···
 	unsigned long reclaimed;
 	int loop = 0;
 	struct mem_cgroup_tree_per_zone *mctz;
-	unsigned long long excess;
+	unsigned long excess;
 	unsigned long nr_scanned;
 
 	if (order > 0)
···
 			} while (1);
 		}
 		__mem_cgroup_remove_exceeded(mz, mctz);
-		excess = res_counter_soft_limit_excess(&mz->memcg->res);
+		excess = soft_limit_excess(mz->memcg);
 		/*
 		 * One school of thought says that we should not add
 		 * back the node to the tree if reclaim returns 0.
···
 static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
 {
 	int node, zid;
-	u64 usage;
 
 	do {
 		/* This is for making all *used* pages to be on LRU. */
···
 		 * right after the check. RES_USAGE should be safe as we always
 		 * charge before adding to the LRU.
 		 */
-		usage = res_counter_read_u64(&memcg->res, RES_USAGE) -
-			res_counter_read_u64(&memcg->kmem, RES_USAGE);
-	} while (usage > 0);
+	} while (page_counter_read(&memcg->memory) -
+		 page_counter_read(&memcg->kmem) > 0);
 }
 
 /*
···
 	/* we call try-to-free pages for make this cgroup empty */
 	lru_add_drain_all();
 	/* try to free all pages in this cgroup */
-	while (nr_retries && res_counter_read_u64(&memcg->res, RES_USAGE) > 0) {
+	while (nr_retries && page_counter_read(&memcg->memory)) {
 		int progress;
 
 		if (signal_pending(current))
···
 	return retval;
 }
 
-static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *memcg,
-					       enum mem_cgroup_stat_index idx)
+static unsigned long tree_stat(struct mem_cgroup *memcg,
+			       enum mem_cgroup_stat_index idx)
 {
 	struct mem_cgroup *iter;
 	long val = 0;
···
 {
 	u64 val;
 
-	if (!mem_cgroup_is_root(memcg)) {
+	if (mem_cgroup_is_root(memcg)) {
+		val = tree_stat(memcg, MEM_CGROUP_STAT_CACHE);
+		val += tree_stat(memcg, MEM_CGROUP_STAT_RSS);
+		if (swap)
+			val += tree_stat(memcg, MEM_CGROUP_STAT_SWAP);
+	} else {
 		if (!swap)
-			return res_counter_read_u64(&memcg->res, RES_USAGE);
+			val = page_counter_read(&memcg->memory);
 		else
-			return res_counter_read_u64(&memcg->memsw, RES_USAGE);
+			val = page_counter_read(&memcg->memsw);
 	}
-
-	/*
-	 * Transparent hugepages are still accounted for in MEM_CGROUP_STAT_RSS
-	 * as well as in MEM_CGROUP_STAT_RSS_HUGE.
-	 */
-	val = mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_CACHE);
-	val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_RSS);
-
-	if (swap)
-		val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_SWAP);
-
 	return val << PAGE_SHIFT;
 }
 
+enum {
+	RES_USAGE,
+	RES_LIMIT,
+	RES_MAX_USAGE,
+	RES_FAILCNT,
+	RES_SOFT_LIMIT,
+};
 
 static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
 			       struct cftype *cft)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
-	enum res_type type = MEMFILE_TYPE(cft->private);
-	int name = MEMFILE_ATTR(cft->private);
+	struct page_counter *counter;
 
-	switch (type) {
+	switch (MEMFILE_TYPE(cft->private)) {
 	case _MEM:
-		if (name == RES_USAGE)
-			return mem_cgroup_usage(memcg, false);
-		return res_counter_read_u64(&memcg->res, name);
-	case _MEMSWAP:
-		if (name == RES_USAGE)
-			return mem_cgroup_usage(memcg, true);
-		return res_counter_read_u64(&memcg->memsw, name);
-	case _KMEM:
-		return res_counter_read_u64(&memcg->kmem, name);
+		counter = &memcg->memory;
 		break;
+	case _MEMSWAP:
+		counter = &memcg->memsw;
+		break;
+	case _KMEM:
+		counter = &memcg->kmem;
+		break;
+	default:
+		BUG();
+	}
+
+	switch (MEMFILE_ATTR(cft->private)) {
+	case RES_USAGE:
+		if (counter == &memcg->memory)
+			return mem_cgroup_usage(memcg, false);
+		if (counter == &memcg->memsw)
+			return mem_cgroup_usage(memcg, true);
+		return (u64)page_counter_read(counter) * PAGE_SIZE;
+	case RES_LIMIT:
+		return (u64)counter->limit * PAGE_SIZE;
+	case RES_MAX_USAGE:
+		return (u64)counter->watermark * PAGE_SIZE;
+	case RES_FAILCNT:
+		return counter->failcnt;
+	case RES_SOFT_LIMIT:
+		return (u64)memcg->soft_limit * PAGE_SIZE;
 	default:
 		BUG();
 	}
···
 #ifdef CONFIG_MEMCG_KMEM
 /* should be called with activate_kmem_mutex held */
 static int __memcg_activate_kmem(struct mem_cgroup *memcg,
-				 unsigned long long limit)
+				 unsigned long nr_pages)
 {
 	int err = 0;
 	int memcg_id;
···
 	 * We couldn't have accounted to this cgroup, because it hasn't got the
 	 * active bit set yet, so this should succeed.
 	 */
-	err = res_counter_set_limit(&memcg->kmem, limit);
+	err = page_counter_limit(&memcg->kmem, nr_pages);
 	VM_BUG_ON(err);
 
 	static_key_slow_inc(&memcg_kmem_enabled_key);
···
 }
 
 static int memcg_activate_kmem(struct mem_cgroup *memcg,
-			       unsigned long long limit)
+			       unsigned long nr_pages)
 {
 	int ret;
 
 	mutex_lock(&activate_kmem_mutex);
-	ret = __memcg_activate_kmem(memcg, limit);
+	ret = __memcg_activate_kmem(memcg, nr_pages);
 	mutex_unlock(&activate_kmem_mutex);
 	return ret;
 }
 
 static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
-				   unsigned long long val)
+				   unsigned long limit)
 {
 	int ret;
 
+	mutex_lock(&memcg_limit_mutex);
 	if (!memcg_kmem_is_active(memcg))
-		ret = memcg_activate_kmem(memcg, val);
+		ret = memcg_activate_kmem(memcg, limit);
 	else
-		ret = res_counter_set_limit(&memcg->kmem, val);
+		ret = page_counter_limit(&memcg->kmem, limit);
+	mutex_unlock(&memcg_limit_mutex);
 	return ret;
 }
 
···
 	 * after this point, because it has at least one child already.
 	 */
 	if (memcg_kmem_is_active(parent))
-		ret = __memcg_activate_kmem(memcg, RES_COUNTER_MAX);
+		ret = __memcg_activate_kmem(memcg, PAGE_COUNTER_MAX);
 	mutex_unlock(&activate_kmem_mutex);
 	return ret;
 }
 #else
 static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
-				   unsigned long long val)
+				   unsigned long limit)
 {
 	return -EINVAL;
 }
···
 				char *buf, size_t nbytes, loff_t off)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
-	enum res_type type;
-	int name;
-	unsigned long long val;
+	unsigned long nr_pages;
 	int ret;
 
 	buf = strstrip(buf);
-	type = MEMFILE_TYPE(of_cft(of)->private);
-	name = MEMFILE_ATTR(of_cft(of)->private);
+	ret = page_counter_memparse(buf, &nr_pages);
+	if (ret)
+		return ret;
 
-	switch (name) {
+	switch (MEMFILE_ATTR(of_cft(of)->private)) {
 	case RES_LIMIT:
 		if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
 			ret = -EINVAL;
 			break;
 		}
-		/* This function does all necessary parse...reuse it */
-		ret = res_counter_memparse_write_strategy(buf, &val);
-		if (ret)
+		switch (MEMFILE_TYPE(of_cft(of)->private)) {
+		case _MEM:
+			ret = mem_cgroup_resize_limit(memcg, nr_pages);
 			break;
-		if (type == _MEM)
-			ret = mem_cgroup_resize_limit(memcg, val);
-		else if (type == _MEMSWAP)
-			ret = mem_cgroup_resize_memsw_limit(memcg, val);
-		else if (type == _KMEM)
-			ret = memcg_update_kmem_limit(memcg, val);
-		else
-			return -EINVAL;
+		case _MEMSWAP:
+			ret = mem_cgroup_resize_memsw_limit(memcg, nr_pages);
+			break;
+		case _KMEM:
+			ret = memcg_update_kmem_limit(memcg, nr_pages);
+			break;
+		}
 		break;
 	case RES_SOFT_LIMIT:
-		ret = res_counter_memparse_write_strategy(buf, &val);
-		if (ret)
-			break;
-		/*
-		 * For memsw, soft limits are hard to implement in terms
-		 * of semantics, for now, we support soft limits for
-		 * control without swap
-		 */
-		if (type == _MEM)
-			ret = res_counter_set_soft_limit(&memcg->res, val);
-		else
-			ret = -EINVAL;
-		break;
-	default:
-		ret = -EINVAL; /* should be BUG() ? */
+		memcg->soft_limit = nr_pages;
+		ret = 0;
 		break;
 	}
 	return ret ?: nbytes;
-}
-
-static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
-		unsigned long long *mem_limit, unsigned long long *memsw_limit)
-{
-	unsigned long long min_limit, min_memsw_limit, tmp;
-
-	min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
-	min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
-	if (!memcg->use_hierarchy)
-		goto out;
-
-	while (memcg->css.parent) {
-		memcg = mem_cgroup_from_css(memcg->css.parent);
-		if (!memcg->use_hierarchy)
-			break;
-		tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
-		min_limit = min(min_limit, tmp);
-		tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
-		min_memsw_limit = min(min_memsw_limit, tmp);
-	}
-out:
-	*mem_limit = min_limit;
-	*memsw_limit = min_memsw_limit;
 }
 
 static ssize_t mem_cgroup_reset(struct kernfs_open_file *of, char *buf,
 				size_t nbytes, loff_t off)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
-	int name;
-	enum res_type type;
+	struct page_counter *counter;
 
-	type = MEMFILE_TYPE(of_cft(of)->private);
-	name = MEMFILE_ATTR(of_cft(of)->private);
+	switch (MEMFILE_TYPE(of_cft(of)->private)) {
+	case _MEM:
+		counter = &memcg->memory;
+		break;
+	case _MEMSWAP:
+		counter = &memcg->memsw;
+		break;
+	case _KMEM:
+		counter = &memcg->kmem;
+		break;
+	default:
+		BUG();
+	}
 
-	switch (name) {
+	switch (MEMFILE_ATTR(of_cft(of)->private)) {
 	case RES_MAX_USAGE:
-		if (type == _MEM)
-			res_counter_reset_max(&memcg->res);
-		else if (type == _MEMSWAP)
-			res_counter_reset_max(&memcg->memsw);
-		else if (type == _KMEM)
-			res_counter_reset_max(&memcg->kmem);
-		else
-			return -EINVAL;
+		page_counter_reset_watermark(counter);
 		break;
 	case RES_FAILCNT:
-		if (type == _MEM)
-			res_counter_reset_failcnt(&memcg->res);
-		else if (type == _MEMSWAP)
-			res_counter_reset_failcnt(&memcg->memsw);
-		else if (type == _KMEM)
-			res_counter_reset_failcnt(&memcg->kmem);
-		else
-			return -EINVAL;
+		counter->failcnt = 0;
 		break;
+	default:
+		BUG();
 	}
 
 	return nbytes;
···
 static int memcg_stat_show(struct seq_file *m, void *v)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
+	unsigned long memory, memsw;
 	struct mem_cgroup *mi;
 	unsigned int i;
 
···
 			   mem_cgroup_nr_lru_pages(memcg, BIT(i)) * PAGE_SIZE);
 
 	/* Hierarchical information */
-	{
-		unsigned long long limit, memsw_limit;
-		memcg_get_hierarchical_limit(memcg, &limit, &memsw_limit);
-		seq_printf(m, "hierarchical_memory_limit %llu\n", limit);
-		if (do_swap_account)
-			seq_printf(m, "hierarchical_memsw_limit %llu\n",
-				   memsw_limit);
+	memory = memsw = PAGE_COUNTER_MAX;
+	for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) {
+		memory = min(memory, mi->memory.limit);
+		memsw = min(memsw, mi->memsw.limit);
 	}
+	seq_printf(m, "hierarchical_memory_limit %llu\n",
+		   (u64)memory * PAGE_SIZE);
+	if (do_swap_account)
+		seq_printf(m, "hierarchical_memsw_limit %llu\n",
+			   (u64)memsw * PAGE_SIZE);
 
 	for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
 		long long val = 0;
···
 static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
 {
 	struct mem_cgroup_threshold_ary *t;
-	u64 usage;
+	unsigned long usage;
 	int i;
 
 	rcu_read_lock();
···
 {
 	struct mem_cgroup_thresholds *thresholds;
 	struct mem_cgroup_threshold_ary *new;
-	u64 threshold, usage;
+	unsigned long threshold;
+	unsigned long usage;
 	int i, size, ret;
 
-	ret = res_counter_memparse_write_strategy(args, &threshold);
+	ret = page_counter_memparse(args, &threshold);
 	if (ret)
 		return ret;
 
···
 {
 	struct mem_cgroup_thresholds *thresholds;
 	struct mem_cgroup_threshold_ary *new;
-	u64 usage;
+	unsigned long usage;
 	int i, j, size;
 
 	mutex_lock(&memcg->thresholds_lock);
···
 
 	memcg_kmem_mark_dead(memcg);
 
-	if (res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0)
+	if (page_counter_read(&memcg->kmem))
 		return;
 
 	if (memcg_kmem_test_and_clear_dead(memcg))
···
  */
 struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
 {
-	if (!memcg->res.parent)
+	if (!memcg->memory.parent)
 		return NULL;
-	return mem_cgroup_from_res_counter(memcg->res.parent, res);
+	return mem_cgroup_from_counter(memcg->memory.parent, memory);
 }
 EXPORT_SYMBOL(parent_mem_cgroup);
 
···
 	/* root ? */
 	if (parent_css == NULL) {
 		root_mem_cgroup = memcg;
-		res_counter_init(&memcg->res, NULL);
-		res_counter_init(&memcg->memsw, NULL);
-		res_counter_init(&memcg->kmem, NULL);
+		page_counter_init(&memcg->memory, NULL);
+		page_counter_init(&memcg->memsw, NULL);
+		page_counter_init(&memcg->kmem, NULL);
 	}
 
 	memcg->last_scanned_node = MAX_NUMNODES;
···
 	memcg->swappiness = mem_cgroup_swappiness(parent);
 
 	if (parent->use_hierarchy) {
-		res_counter_init(&memcg->res, &parent->res);
-		res_counter_init(&memcg->memsw, &parent->memsw);
-		res_counter_init(&memcg->kmem, &parent->kmem);
+		page_counter_init(&memcg->memory, &parent->memory);
+		page_counter_init(&memcg->memsw, &parent->memsw);
+		page_counter_init(&memcg->kmem, &parent->kmem);
 
 		/*
 		 * No need to take a reference to the parent because cgroup
 		 * core guarantees its existence.
 		 */
 	} else {
-		res_counter_init(&memcg->res, NULL);
-		res_counter_init(&memcg->memsw, NULL);
-		res_counter_init(&memcg->kmem, NULL);
+		page_counter_init(&memcg->memory, NULL);
+		page_counter_init(&memcg->memsw, NULL);
+		page_counter_init(&memcg->kmem, NULL);
 		/*
 		 * Deeper hierachy with use_hierarchy == false doesn't make
 		 * much sense so let cgroup subsystem know about this
···
 	/*
 	 * XXX: css_offline() would be where we should reparent all
 	 * memory to prepare the cgroup for destruction.  However,
-	 * memcg does not do css_tryget_online() and res_counter charging
+	 * memcg does not do css_tryget_online() and page_counter charging
 	 * under the same RCU lock region, which means that charging
 	 * could race with offlining.  Offlining only happens to
 	 * cgroups with no tasks in them but charges can show up
···
 	 * call_rcu()
 	 *   offline_css()
 	 *     reparent_charges()
-	 *                           res_counter_charge()
+	 *                           page_counter_try_charge()
 	 *                           css_put()
 	 *                             css_free()
 	 *                           pc->mem_cgroup = dead memcg
···
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
-	mem_cgroup_resize_limit(memcg, ULLONG_MAX);
-	mem_cgroup_resize_memsw_limit(memcg, ULLONG_MAX);
-	memcg_update_kmem_limit(memcg, ULLONG_MAX);
-	res_counter_set_soft_limit(&memcg->res, ULLONG_MAX);
+	mem_cgroup_resize_limit(memcg, PAGE_COUNTER_MAX);
+	mem_cgroup_resize_memsw_limit(memcg, PAGE_COUNTER_MAX);
+	memcg_update_kmem_limit(memcg, PAGE_COUNTER_MAX);
+	memcg->soft_limit = 0;
 }
 
 #ifdef CONFIG_MMU
···
 	if (mc.moved_swap) {
 		/* uncharge swap account from the old cgroup */
 		if (!mem_cgroup_is_root(mc.from))
-			res_counter_uncharge(&mc.from->memsw,
-					     PAGE_SIZE * mc.moved_swap);
+			page_counter_uncharge(&mc.from->memsw, mc.moved_swap);
+
+		/*
+		 * we charged both to->memory and to->memsw, so we
+		 * should uncharge to->memory.
+		 */
+		if (!mem_cgroup_is_root(mc.to))
+			page_counter_uncharge(&mc.to->memory, mc.moved_swap);
 
 		for (i = 0; i < mc.moved_swap; i++)
 			css_put(&mc.from->css);
 
-		/*
-		 * we charged both to->res and to->memsw, so we should
-		 * uncharge to->res.
-		 */
-		if (!mem_cgroup_is_root(mc.to))
-			res_counter_uncharge(&mc.to->res,
-					     PAGE_SIZE * mc.moved_swap);
 		/* we've already done css_get(mc.to) */
 		mc.moved_swap = 0;
 	}
···
 	memcg = mem_cgroup_lookup(id);
 	if (memcg) {
 		if (!mem_cgroup_is_root(memcg))
-			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+			page_counter_uncharge(&memcg->memsw, 1);
 		mem_cgroup_swap_statistics(memcg, false);
 		css_put(&memcg->css);
 	}
···
 
 	if (!mem_cgroup_is_root(memcg)) {
 		if (nr_mem)
-			res_counter_uncharge(&memcg->res,
-					     nr_mem * PAGE_SIZE);
+			page_counter_uncharge(&memcg->memory, nr_mem);
 		if (nr_memsw)
-			res_counter_uncharge(&memcg->memsw,
-					     nr_memsw * PAGE_SIZE);
+			page_counter_uncharge(&memcg->memsw, nr_memsw);
 		memcg_oom_recover(memcg);
 	}
 

mm/page_counter.c

···
+/*
+ * Lockless hierarchical page accounting & limiting
+ *
+ * Copyright (C) 2014 Red Hat, Inc., Johannes Weiner
+ */
+
+#include <linux/page_counter.h>
+#include <linux/atomic.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/sched.h>
+#include <linux/bug.h>
+#include <asm/page.h>
+
+/**
+ * page_counter_cancel - take pages out of the local counter
+ * @counter: counter
+ * @nr_pages: number of pages to cancel
+ *
+ * Returns whether there are remaining pages in the counter.
+ */
+int page_counter_cancel(struct page_counter *counter, unsigned long nr_pages)
+{
+	long new;
+
+	new = atomic_long_sub_return(nr_pages, &counter->count);
+
+	/* More uncharges than charges? */
+	WARN_ON_ONCE(new < 0);
+
+	return new > 0;
+}
+
+/**
+ * page_counter_charge - hierarchically charge pages
+ * @counter: counter
+ * @nr_pages: number of pages to charge
+ *
+ * NOTE: This does not consider any configured counter limits.
+ */
+void page_counter_charge(struct page_counter *counter, unsigned long nr_pages)
+{
+	struct page_counter *c;
+
+	for (c = counter; c; c = c->parent) {
+		long new;
+
+		new = atomic_long_add_return(nr_pages, &c->count);
+		/*
+		 * This is indeed racy, but we can live with some
+		 * inaccuracy in the watermark.
+		 */
+		if (new > c->watermark)
+			c->watermark = new;
+	}
+}
+
+/**
+ * page_counter_try_charge - try to hierarchically charge pages
+ * @counter: counter
+ * @nr_pages: number of pages to charge
+ * @fail: points first counter to hit its limit, if any
+ *
+ * Returns 0 on success, or -ENOMEM and @fail if the counter or one of
+ * its ancestors has hit its configured limit.
+ */
+int page_counter_try_charge(struct page_counter *counter,
+			    unsigned long nr_pages,
+			    struct page_counter **fail)
+{
+	struct page_counter *c;
+
+	for (c = counter; c; c = c->parent) {
+		long new;
+		/*
+		 * Charge speculatively to avoid an expensive CAS.  If
+		 * a bigger charge fails, it might falsely lock out a
+		 * racing smaller charge and send it into reclaim
+		 * early, but the error is limited to the difference
+		 * between the two sizes, which is less than 2M/4M in
+		 * case of a THP locking out a regular page charge.
+		 *
+		 * The atomic_long_add_return() implies a full memory
+		 * barrier between incrementing the count and reading
+		 * the limit.  When racing with page_counter_limit(),
+		 * we either see the new limit or the setter sees the
+		 * counter has changed and retries.
+		 */
+		new = atomic_long_add_return(nr_pages, &c->count);
+		if (new > c->limit) {
+			atomic_long_sub(nr_pages, &c->count);
+			/*
+			 * This is racy, but we can live with some
+			 * inaccuracy in the failcnt.
+			 */
+			c->failcnt++;
+			*fail = c;
+			goto failed;
+		}
+		/*
+		 * Just like with failcnt, we can live with some
+		 * inaccuracy in the watermark.
+		 */
+		if (new > c->watermark)
+			c->watermark = new;
+	}
+	return 0;
+
+failed:
+	for (c = counter; c != *fail; c = c->parent)
+		page_counter_cancel(c, nr_pages);
+
+	return -ENOMEM;
+}
+
+/**
+ * page_counter_uncharge - hierarchically uncharge pages
+ * @counter: counter
+ * @nr_pages: number of pages to uncharge
+ *
+ * Returns whether there are remaining charges in @counter.
+ */
+int page_counter_uncharge(struct page_counter *counter, unsigned long nr_pages)
+{
+	struct page_counter *c;
+	int ret = 1;
+
+	for (c = counter; c; c = c->parent) {
+		int remainder;
+
+		remainder = page_counter_cancel(c, nr_pages);
+		if (c == counter && !remainder)
+			ret = 0;
+	}
+
+	return ret;
+}
+
+/**
+ * page_counter_limit - limit the number of pages allowed
+ * @counter: counter
+ * @limit: limit to set
+ *
+ * Returns 0 on success, -EBUSY if the current number of pages on the
+ * counter already exceeds the specified limit.
+ *
+ * The caller must serialize invocations on the same counter.
+ */
+int page_counter_limit(struct page_counter *counter, unsigned long limit)
+{
+	for (;;) {
+		unsigned long old;
+		long count;
+
+		/*
+		 * Update the limit while making sure that it's not
+		 * below the concurrently-changing counter value.
+		 *
+		 * The xchg implies two full memory barriers before
+		 * and after, so the read-swap-read is ordered and
+		 * ensures coherency with page_counter_try_charge():
+		 * that function modifies the count before checking
+		 * the limit, so if it sees the old limit, we see the
+		 * modified counter and retry.
+		 */
+		count = atomic_long_read(&counter->count);
+
+		if (count > limit)
+			return -EBUSY;
+
+		old = xchg(&counter->limit, limit);
+
+		if (atomic_long_read(&counter->count) <= count)
+			return 0;
+
+		counter->limit = old;
+		cond_resched();
+	}
+}
+
+/**
+ * page_counter_memparse - memparse() for page counter limits
+ * @buf: string to parse
+ * @nr_pages: returns the result in number of pages
+ *
+ * Returns -EINVAL, or 0 and @nr_pages on success.  @nr_pages will be
+ * limited to %PAGE_COUNTER_MAX.
+ */
+int page_counter_memparse(const char *buf, unsigned long *nr_pages)
+{
+	char unlimited[] = "-1";
+	char *end;
+	u64 bytes;
+
+	if (!strncmp(buf, unlimited, sizeof(unlimited))) {
+		*nr_pages = PAGE_COUNTER_MAX;
+		return 0;
+	}
+
+	bytes = memparse(buf, &end);
+	if (*end != '\0')
+		return -EINVAL;
+
+	*nr_pages = min(bytes / PAGE_SIZE, (u64)PAGE_COUNTER_MAX);
+
+	return 0;
+}

net/ipv4/tcp_memcontrol.c

···
 int tcp_init_cgroup(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
 	/*
-	 * The root cgroup does not use res_counters, but rather,
+	 * The root cgroup does not use page_counters, but rather,
 	 * rely on the data already collected by the network
 	 * subsystem
 	 */
-	struct res_counter *res_parent = NULL;
-	struct cg_proto *cg_proto, *parent_cg;
 	struct mem_cgroup *parent = parent_mem_cgroup(memcg);
+	struct page_counter *counter_parent = NULL;
+	struct cg_proto *cg_proto, *parent_cg;
 
 	cg_proto = tcp_prot.proto_cgroup(memcg);
 	if (!cg_proto)
···
 
 	parent_cg = tcp_prot.proto_cgroup(parent);
 	if (parent_cg)
-		res_parent = &parent_cg->memory_allocated;
+		counter_parent = &parent_cg->memory_allocated;
 
-	res_counter_init(&cg_proto->memory_allocated, res_parent);
+	page_counter_init(&cg_proto->memory_allocated, counter_parent);
 	percpu_counter_init(&cg_proto->sockets_allocated, 0, GFP_KERNEL);
 
 	return 0;
···
 }
 EXPORT_SYMBOL(tcp_destroy_cgroup);
 
-static int tcp_update_limit(struct mem_cgroup *memcg, u64 val)
+static int tcp_update_limit(struct mem_cgroup *memcg, unsigned long nr_pages)
 {
 	struct cg_proto *cg_proto;
 	int i;
···
 	if (!cg_proto)
 		return -EINVAL;
 
-	if (val > RES_COUNTER_MAX)
-		val = RES_COUNTER_MAX;
-
-	ret = res_counter_set_limit(&cg_proto->memory_allocated, val);
+	ret = page_counter_limit(&cg_proto->memory_allocated, nr_pages);
 	if (ret)
 		return ret;
 
 	for (i = 0; i < 3; i++)
-		cg_proto->sysctl_mem[i] = min_t(long, val >> PAGE_SHIFT,
+		cg_proto->sysctl_mem[i] = min_t(long, nr_pages,
 						sysctl_tcp_mem[i]);
 
-	if (val == RES_COUNTER_MAX)
+	if (nr_pages == PAGE_COUNTER_MAX)
 		clear_bit(MEMCG_SOCK_ACTIVE, &cg_proto->flags);
-	else if (val != RES_COUNTER_MAX) {
+	else {
 		/*
 		 * The active bit needs to be written after the static_key
 		 * update. This is what guarantees that the socket activation
···
 	return 0;
 }
 
+enum {
+	RES_USAGE,
+	RES_LIMIT,
+	RES_MAX_USAGE,
+	RES_FAILCNT,
+};
+
+static DEFINE_MUTEX(tcp_limit_mutex);
+
 static ssize_t tcp_cgroup_write(struct kernfs_open_file *of,
 				char *buf, size_t nbytes, loff_t off)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
-	unsigned long long val;
+	unsigned long nr_pages;
 	int ret = 0;
 
 	buf = strstrip(buf);
···
 	switch (of_cft(of)->private) {
 	case RES_LIMIT:
 		/* see memcontrol.c */
-		ret = res_counter_memparse_write_strategy(buf, &val);
+		ret = page_counter_memparse(buf, &nr_pages);
 		if (ret)
 			break;
-		ret = tcp_update_limit(memcg, val);
+		mutex_lock(&tcp_limit_mutex);
+		ret = tcp_update_limit(memcg, nr_pages);
+		mutex_unlock(&tcp_limit_mutex);
 		break;
 	default:
 		ret = -EINVAL;
···
 	return ret ?: nbytes;
 }
 
-static u64 tcp_read_stat(struct mem_cgroup *memcg, int type, u64 default_val)
-{
-	struct cg_proto *cg_proto;
-
-	cg_proto = tcp_prot.proto_cgroup(memcg);
-	if (!cg_proto)
-		return default_val;
-
-	return res_counter_read_u64(&cg_proto->memory_allocated, type);
-}
-
-static u64 tcp_read_usage(struct mem_cgroup *memcg)
-{
-	struct cg_proto *cg_proto;
-
-	cg_proto = tcp_prot.proto_cgroup(memcg);
-	if (!cg_proto)
-		return atomic_long_read(&tcp_memory_allocated) << PAGE_SHIFT;
-
-	return res_counter_read_u64(&cg_proto->memory_allocated, RES_USAGE);
-}
-
 static u64 tcp_cgroup_read(struct cgroup_subsys_state *css, struct cftype *cft)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
+	struct cg_proto *cg_proto = tcp_prot.proto_cgroup(memcg);
 	u64 val;
 
 	switch (cft->private) {
 	case RES_LIMIT:
-		val = tcp_read_stat(memcg, RES_LIMIT, RES_COUNTER_MAX);
+		if (!cg_proto)
+			return PAGE_COUNTER_MAX;
+		val = cg_proto->memory_allocated.limit;
+		val *= PAGE_SIZE;
 		break;
 	case RES_USAGE:
-		val = tcp_read_usage(memcg);
+		if (!cg_proto)
+			val = atomic_long_read(&tcp_memory_allocated);
+		else
+			val = page_counter_read(&cg_proto->memory_allocated);
+		val *= PAGE_SIZE;
 		break;
 	case RES_FAILCNT:
+		if (!cg_proto)
+			return 0;
+		val = cg_proto->memory_allocated.failcnt;
+		break;
 	case RES_MAX_USAGE:
-		val = tcp_read_stat(memcg, cft->private, 0);
+		if (!cg_proto)
+			return 0;
+		val = cg_proto->memory_allocated.watermark;
+		val *= PAGE_SIZE;
 		break;
 	default:
 		BUG();
···
 
 	switch (of_cft(of)->private) {
 	case RES_MAX_USAGE:
-		res_counter_reset_max(&cg_proto->memory_allocated);
+		page_counter_reset_watermark(&cg_proto->memory_allocated);
 		break;
 	case RES_FAILCNT:
-		res_counter_reset_failcnt(&cg_proto->memory_allocated);
+		cg_proto->memory_allocated.failcnt = 0;
 		break;
 	}