[PATCH 0/5] memcg: towards I/O aware memcg v6.

[PATCH 0/5] memcg: towards I/O aware memcg v6.

[KAMEZAWA Hiroyuki]

This is v6. Thank you all for kindly reviews.

Major changes from v5 is
 a) changed ID allocation logic. Maybe much clearer than v6.
 b) fixed typos and bugs.

Patch brief view:
 1. changes css ID allocation in kernel/cgroup.c
 2. use ID-array in memcg.
 3. record ID to page_cgroup rather than pointer.
 4. make update_file_mapped to be RCU aware routine instead of spinlock.
 5. make update_file_mapped as general-purpose function.


Thanks,
-Kame

[PATCH 0/5] memcg: towards I/O aware memcg v6.

[KAMEZAWA Hiroyuki]

This is v6. Thank you all for kindly reviews.

Major changes from v5 is
 a) changed ID allocation logic. Maybe much clearer than v6.
 b) fixed typos and bugs.

Patch brief view:
 1. changes css ID allocation in kernel/cgroup.c
 2. use ID-array in memcg.
 3. record ID to page_cgroup rather than pointer.
 4. make update_file_mapped to be RCU aware routine instead of spinlock.
 5. make update_file_mapped as general-purpose function.


Thanks,
-Kame

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[PATCH 1/5] cgroup: do ID allocation under css allocator.

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Now, css'id is allocated after ->create() is called. But to make use of ID
in ->create(), it should be available before ->create().

In another thinking, considering the ID is tightly coupled with "css",
it should be allocated when "css" is allocated.
This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
memory and blkio are useing ID. (To support complicated hierarchy walk.)

ID will be used in mem cgroup's ->create(), later.

Note:
If someone changes rules of css allocation, ID allocation should be moved too.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 block/blk-cgroup.c     |    9 ++++++++
 include/linux/cgroup.h |   16 ++++++++-------
 kernel/cgroup.c        |   50 ++++++++++++++-----------------------------------
 mm/memcontrol.c        |    5 ++++
 4 files changed, 38 insertions(+), 42 deletions(-)

Index: mmotm-0811/kernel/cgroup.c
===================================================================
--- mmotm-0811.orig/kernel/cgroup.c
+++ mmotm-0811/kernel/cgroup.c
@@ -289,9 +289,6 @@ struct cg_cgroup_link {
 static struct css_set init_css_set;
 static struct cg_cgroup_link init_css_set_link;
 
-static int cgroup_init_idr(struct cgroup_subsys *ss,
-			   struct cgroup_subsys_state *css);
-
 /* css_set_lock protects the list of css_set objects, and the
  * chain of tasks off each css_set.  Nests outside task->alloc_lock
  * due to cgroup_iter_start() */
@@ -770,9 +767,6 @@ static struct backing_dev_info cgroup_ba
 	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
-static int alloc_css_id(struct cgroup_subsys *ss,
-			struct cgroup *parent, struct cgroup *child);
-
 static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
 {
 	struct inode *inode = new_inode(sb);
@@ -3257,7 +3251,8 @@ static void init_cgroup_css(struct cgrou
 	css->cgroup = cgrp;
 	atomic_set(&css->refcnt, 1);
 	css->flags = 0;
-	css->id = NULL;
+	if (!ss->use_id)
+		css->id = NULL;
 	if (cgrp == dummytop)
 		set_bit(CSS_ROOT, &css->flags);
 	BUG_ON(cgrp->subsys[ss->subsys_id]);
@@ -3342,12 +3337,6 @@ static long cgroup_create(struct cgroup 
 			goto err_destroy;
 		}
 		init_cgroup_css(css, ss, cgrp);
-		if (ss->use_id) {
-			err = alloc_css_id(ss, parent, cgrp);
-			if (err)
-				goto err_destroy;
-		}
-		/* At error, ->destroy() callback has to free assigned ID. */
 	}
 
 	cgroup_lock_hierarchy(root);
@@ -3709,17 +3698,6 @@ int __init_or_module cgroup_load_subsys(
 
 	/* our new subsystem will be attached to the dummy hierarchy. */
 	init_cgroup_css(css, ss, dummytop);
-	/* init_idr must be after init_cgroup_css because it sets css->id. */
-	if (ss->use_id) {
-		int ret = cgroup_init_idr(ss, css);
-		if (ret) {
-			dummytop->subsys[ss->subsys_id] = NULL;
-			ss->destroy(ss, dummytop);
-			subsys[i] = NULL;
-			mutex_unlock(&cgroup_mutex);
-			return ret;
-		}
-	}
 
 	/*
 	 * Now we need to entangle the css into the existing css_sets. unlike
@@ -3888,8 +3866,6 @@ int __init cgroup_init(void)
 		struct cgroup_subsys *ss = subsys[i];
 		if (!ss->early_init)
 			cgroup_init_subsys(ss);
-		if (ss->use_id)
-			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
 	}
 
 	/* Add init_css_set to the hash table */
@@ -4603,8 +4579,8 @@ err_out:
 
 }
 
-static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
-					    struct cgroup_subsys_state *rootcss)
+static int cgroup_init_idr(struct cgroup_subsys *ss,
+			    struct cgroup_subsys_state *rootcss)
 {
 	struct css_id *newid;
 
@@ -4616,21 +4592,25 @@ static int __init_or_module cgroup_init_
 		return PTR_ERR(newid);
 
 	newid->stack[0] = newid->id;
-	newid->css = rootcss;
-	rootcss->id = newid;
+	rcu_assign_pointer(newid->css, rootcss);
+	rcu_assign_pointer(rootcss->id, newid);
 	return 0;
 }
 
-static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
-			struct cgroup *child)
+int alloc_css_id(struct cgroup_subsys *ss,
+	struct cgroup *cgrp, struct cgroup_subsys_state *css)
 {
 	int subsys_id, i, depth = 0;
-	struct cgroup_subsys_state *parent_css, *child_css;
+	struct cgroup_subsys_state *parent_css;
+	struct cgroup *parent;
 	struct css_id *child_id, *parent_id;
 
+	if (cgrp == dummytop)
+		return cgroup_init_idr(ss, css);
+
+	parent = cgrp->parent;
 	subsys_id = ss->subsys_id;
 	parent_css = parent->subsys[subsys_id];
-	child_css = child->subsys[subsys_id];
 	parent_id = parent_css->id;
 	depth = parent_id->depth + 1;
 
@@ -4645,7 +4625,7 @@ static int alloc_css_id(struct cgroup_su
 	 * child_id->css pointer will be set after this cgroup is available
 	 * see cgroup_populate_dir()
 	 */
-	rcu_assign_pointer(child_css->id, child_id);
+	rcu_assign_pointer(css->id, child_id);
 
 	return 0;
 }
Index: mmotm-0811/include/linux/cgroup.h
===================================================================
--- mmotm-0811.orig/include/linux/cgroup.h
+++ mmotm-0811/include/linux/cgroup.h
@@ -583,9 +583,11 @@ int cgroup_attach_task_current_cg(struct
 /*
  * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
  * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
- * CSS ID is assigned at cgroup allocation (create) automatically
- * and removed when subsys calls free_css_id() function. This is because
- * the lifetime of cgroup_subsys_state is subsys's matter.
+ * CSS ID must be assigned by subsys itself at cgroup creation and deleted
+ * when subsys calls free_css_id() function. This is because the life time of
+ * of cgroup_subsys_state is subsys's matter.
+ *
+ * ID->css look up is available after cgroup's directory is populated.
  *
  * Looking up and scanning function should be called under rcu_read_lock().
  * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
@@ -593,10 +595,10 @@ int cgroup_attach_task_current_cg(struct
  * destroyed". The caller should check css and cgroup's status.
  */
 
-/*
- * Typically Called at ->destroy(), or somewhere the subsys frees
- * cgroup_subsys_state.
- */
+/* Should be called in ->create() by subsys itself */
+int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *newgr,
+		struct cgroup_subsys_state *css);
+/* Typically Called at ->destroy(), or somewhere the subsys frees css */
 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
 
 /* Find a cgroup_subsys_state which has given ID */
Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -4141,6 +4141,11 @@ mem_cgroup_create(struct cgroup_subsys *
 		if (alloc_mem_cgroup_per_zone_info(mem, node))
 			goto free_out;
 
+	error = alloc_css_id(ss, cont, &mem->css);
+	if (error)
+		goto free_out;
+	/* Here, css_id(&mem->css) works. but css_lookup(id)->mem doesn't */
+
 	/* root ? */
 	if (cont->parent == NULL) {
 		int cpu;
Index: mmotm-0811/block/blk-cgroup.c
===================================================================
--- mmotm-0811.orig/block/blk-cgroup.c
+++ mmotm-0811/block/blk-cgroup.c
@@ -958,9 +958,13 @@ blkiocg_create(struct cgroup_subsys *sub
 {
 	struct blkio_cgroup *blkcg;
 	struct cgroup *parent = cgroup->parent;
+	int ret;
 
 	if (!parent) {
 		blkcg = &blkio_root_cgroup;
+		ret = alloc_css_id(subsys, cgroup, &blkcg->css);
+		if (ret)
+			return ERR_PTR(ret);
 		goto done;
 	}
 
@@ -971,6 +975,11 @@ blkiocg_create(struct cgroup_subsys *sub
 	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 	if (!blkcg)
 		return ERR_PTR(-ENOMEM);
+	ret = alloc_css_id(subsys, cgroup, &blkcg->css);
+	if (ret) {
+		kfree(blkcg);
+		return ERR_PTR(ret);
+	}
 
 	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
 done:

[PATCH 1/5] cgroup: do ID allocation under css allocator.

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Now, css'id is allocated after ->create() is called. But to make use of ID
in ->create(), it should be available before ->create().

In another thinking, considering the ID is tightly coupled with "css",
it should be allocated when "css" is allocated.
This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
memory and blkio are useing ID. (To support complicated hierarchy walk.)

ID will be used in mem cgroup's ->create(), later.

Note:
If someone changes rules of css allocation, ID allocation should be moved too.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 block/blk-cgroup.c     |    9 ++++++++
 include/linux/cgroup.h |   16 ++++++++-------
 kernel/cgroup.c        |   50 ++++++++++++++-----------------------------------
 mm/memcontrol.c        |    5 ++++
 4 files changed, 38 insertions(+), 42 deletions(-)

Index: mmotm-0811/kernel/cgroup.c
===================================================================
--- mmotm-0811.orig/kernel/cgroup.c
+++ mmotm-0811/kernel/cgroup.c
@@ -289,9 +289,6 @@ struct cg_cgroup_link {
 static struct css_set init_css_set;
 static struct cg_cgroup_link init_css_set_link;
 
-static int cgroup_init_idr(struct cgroup_subsys *ss,
-			   struct cgroup_subsys_state *css);
-
 /* css_set_lock protects the list of css_set objects, and the
  * chain of tasks off each css_set.  Nests outside task->alloc_lock
  * due to cgroup_iter_start() */
@@ -770,9 +767,6 @@ static struct backing_dev_info cgroup_ba
 	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
-static int alloc_css_id(struct cgroup_subsys *ss,
-			struct cgroup *parent, struct cgroup *child);
-
 static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
 {
 	struct inode *inode = new_inode(sb);
@@ -3257,7 +3251,8 @@ static void init_cgroup_css(struct cgrou
 	css->cgroup = cgrp;
 	atomic_set(&css->refcnt, 1);
 	css->flags = 0;
-	css->id = NULL;
+	if (!ss->use_id)
+		css->id = NULL;
 	if (cgrp == dummytop)
 		set_bit(CSS_ROOT, &css->flags);
 	BUG_ON(cgrp->subsys[ss->subsys_id]);
@@ -3342,12 +3337,6 @@ static long cgroup_create(struct cgroup 
 			goto err_destroy;
 		}
 		init_cgroup_css(css, ss, cgrp);
-		if (ss->use_id) {
-			err = alloc_css_id(ss, parent, cgrp);
-			if (err)
-				goto err_destroy;
-		}
-		/* At error, ->destroy() callback has to free assigned ID. */
 	}
 
 	cgroup_lock_hierarchy(root);
@@ -3709,17 +3698,6 @@ int __init_or_module cgroup_load_subsys(
 
 	/* our new subsystem will be attached to the dummy hierarchy. */
 	init_cgroup_css(css, ss, dummytop);
-	/* init_idr must be after init_cgroup_css because it sets css->id. */
-	if (ss->use_id) {
-		int ret = cgroup_init_idr(ss, css);
-		if (ret) {
-			dummytop->subsys[ss->subsys_id] = NULL;
-			ss->destroy(ss, dummytop);
-			subsys[i] = NULL;
-			mutex_unlock(&cgroup_mutex);
-			return ret;
-		}
-	}
 
 	/*
 	 * Now we need to entangle the css into the existing css_sets. unlike
@@ -3888,8 +3866,6 @@ int __init cgroup_init(void)
 		struct cgroup_subsys *ss = subsys[i];
 		if (!ss->early_init)
 			cgroup_init_subsys(ss);
-		if (ss->use_id)
-			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
 	}
 
 	/* Add init_css_set to the hash table */
@@ -4603,8 +4579,8 @@ err_out:
 
 }
 
-static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
-					    struct cgroup_subsys_state *rootcss)
+static int cgroup_init_idr(struct cgroup_subsys *ss,
+			    struct cgroup_subsys_state *rootcss)
 {
 	struct css_id *newid;
 
@@ -4616,21 +4592,25 @@ static int __init_or_module cgroup_init_
 		return PTR_ERR(newid);
 
 	newid->stack[0] = newid->id;
-	newid->css = rootcss;
-	rootcss->id = newid;
+	rcu_assign_pointer(newid->css, rootcss);
+	rcu_assign_pointer(rootcss->id, newid);
 	return 0;
 }
 
-static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
-			struct cgroup *child)
+int alloc_css_id(struct cgroup_subsys *ss,
+	struct cgroup *cgrp, struct cgroup_subsys_state *css)
 {
 	int subsys_id, i, depth = 0;
-	struct cgroup_subsys_state *parent_css, *child_css;
+	struct cgroup_subsys_state *parent_css;
+	struct cgroup *parent;
 	struct css_id *child_id, *parent_id;
 
+	if (cgrp == dummytop)
+		return cgroup_init_idr(ss, css);
+
+	parent = cgrp->parent;
 	subsys_id = ss->subsys_id;
 	parent_css = parent->subsys[subsys_id];
-	child_css = child->subsys[subsys_id];
 	parent_id = parent_css->id;
 	depth = parent_id->depth + 1;
 
@@ -4645,7 +4625,7 @@ static int alloc_css_id(struct cgroup_su
 	 * child_id->css pointer will be set after this cgroup is available
 	 * see cgroup_populate_dir()
 	 */
-	rcu_assign_pointer(child_css->id, child_id);
+	rcu_assign_pointer(css->id, child_id);
 
 	return 0;
 }
Index: mmotm-0811/include/linux/cgroup.h
===================================================================
--- mmotm-0811.orig/include/linux/cgroup.h
+++ mmotm-0811/include/linux/cgroup.h
@@ -583,9 +583,11 @@ int cgroup_attach_task_current_cg(struct
 /*
  * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
  * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
- * CSS ID is assigned at cgroup allocation (create) automatically
- * and removed when subsys calls free_css_id() function. This is because
- * the lifetime of cgroup_subsys_state is subsys's matter.
+ * CSS ID must be assigned by subsys itself at cgroup creation and deleted
+ * when subsys calls free_css_id() function. This is because the life time of
+ * of cgroup_subsys_state is subsys's matter.
+ *
+ * ID->css look up is available after cgroup's directory is populated.
  *
  * Looking up and scanning function should be called under rcu_read_lock().
  * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
@@ -593,10 +595,10 @@ int cgroup_attach_task_current_cg(struct
  * destroyed". The caller should check css and cgroup's status.
  */
 
-/*
- * Typically Called at ->destroy(), or somewhere the subsys frees
- * cgroup_subsys_state.
- */
+/* Should be called in ->create() by subsys itself */
+int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *newgr,
+		struct cgroup_subsys_state *css);
+/* Typically Called at ->destroy(), or somewhere the subsys frees css */
 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
 
 /* Find a cgroup_subsys_state which has given ID */
Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -4141,6 +4141,11 @@ mem_cgroup_create(struct cgroup_subsys *
 		if (alloc_mem_cgroup_per_zone_info(mem, node))
 			goto free_out;
 
+	error = alloc_css_id(ss, cont, &mem->css);
+	if (error)
+		goto free_out;
+	/* Here, css_id(&mem->css) works. but css_lookup(id)->mem doesn't */
+
 	/* root ? */
 	if (cont->parent == NULL) {
 		int cpu;
Index: mmotm-0811/block/blk-cgroup.c
===================================================================
--- mmotm-0811.orig/block/blk-cgroup.c
+++ mmotm-0811/block/blk-cgroup.c
@@ -958,9 +958,13 @@ blkiocg_create(struct cgroup_subsys *sub
 {
 	struct blkio_cgroup *blkcg;
 	struct cgroup *parent = cgroup->parent;
+	int ret;
 
 	if (!parent) {
 		blkcg = &blkio_root_cgroup;
+		ret = alloc_css_id(subsys, cgroup, &blkcg->css);
+		if (ret)
+			return ERR_PTR(ret);
 		goto done;
 	}
 
@@ -971,6 +975,11 @@ blkiocg_create(struct cgroup_subsys *sub
 	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 	if (!blkcg)
 		return ERR_PTR(-ENOMEM);
+	ret = alloc_css_id(subsys, cgroup, &blkcg->css);
+	if (ret) {
+		kfree(blkcg);
+		return ERR_PTR(ret);
+	}
 
 	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
 done:

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[PATCH 2/5] memcg: quick memcg lookup array

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Now, memory cgroup has an ID per cgroup and make use of it at
 - hierarchy walk,
 - swap recording.

This patch is for making more use of it. The final purpose is
to replace page_cgroup->mem_cgroup's pointer to an unsigned short.

This patch caches a pointer of memcg in an array. By this, we
don't have to call css_lookup() which requires radix-hash walk.
This saves some amount of memory footprint at lookup memcg via id.

Changelog: 20100825
 - applied comments.

Changelog: 20100811
 - adjusted onto mmotm-2010-08-11
 - fixed RCU related parts.
 - use attach_id() callback.

Changelog: 20100804
 - fixed description in init/Kconfig

Changelog: 20100730
 - fixed rcu_read_unlock() placement.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 init/Kconfig    |   10 +++++++
 mm/memcontrol.c |   75 +++++++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 65 insertions(+), 20 deletions(-)

Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
  */
 struct mem_cgroup {
 	struct cgroup_subsys_state css;
+	int	valid; /* for checking validness under RCU access.*/
 	/*
 	 * the counter to account for memory usage
 	 */
@@ -294,6 +295,29 @@ static bool move_file(void)
 					&mc.to->move_charge_at_immigrate);
 }
 
+/* 0 is unused */
+static atomic_t mem_cgroup_num;
+#define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
+static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
+
+/* Must be called under rcu_read_lock */
+static struct mem_cgroup *id_to_memcg(unsigned short id)
+{
+	struct mem_cgroup *mem;
+	/* see mem_cgroup_free() */
+	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
+	if (likely(mem && mem->valid))
+		return mem;
+	return NULL;
+}
+
+static void register_memcg_id(struct mem_cgroup *mem)
+{
+	int id = css_id(&mem->css);
+	rcu_assign_pointer(mem_cgroups[id], mem);
+	VM_BUG_ON(!mem->valid);
+}
+
 /*
  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
  * limit reclaim to prevent infinite loops, if they ever occur.
@@ -1847,18 +1871,7 @@ static void mem_cgroup_cancel_charge(str
  * it's concern. (dropping refcnt from swap can be called against removed
  * memcg.)
  */
-static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
-{
-	struct cgroup_subsys_state *css;
 
-	/* ID 0 is unused ID */
-	if (!id)
-		return NULL;
-	css = css_lookup(&mem_cgroup_subsys, id);
-	if (!css)
-		return NULL;
-	return container_of(css, struct mem_cgroup, css);
-}
 
 struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
 {
@@ -1879,7 +1892,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr
 		ent.val = page_private(page);
 		id = lookup_swap_cgroup(ent);
 		rcu_read_lock();
-		mem = mem_cgroup_lookup(id);
+		mem = id_to_memcg(id);
 		if (mem && !css_tryget(&mem->css))
 			mem = NULL;
 		rcu_read_unlock();
@@ -2231,7 +2244,7 @@ __mem_cgroup_commit_charge_swapin(struct
 
 		id = swap_cgroup_record(ent, 0);
 		rcu_read_lock();
-		memcg = mem_cgroup_lookup(id);
+		memcg = id_to_memcg(id);
 		if (memcg) {
 			/*
 			 * This recorded memcg can be obsolete one. So, avoid
@@ -2240,9 +2253,10 @@ __mem_cgroup_commit_charge_swapin(struct
 			if (!mem_cgroup_is_root(memcg))
 				res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
 			mem_cgroup_swap_statistics(memcg, false);
+			rcu_read_unlock();
 			mem_cgroup_put(memcg);
-		}
-		rcu_read_unlock();
+		} else
+			rcu_read_unlock();
 	}
 	/*
 	 * At swapin, we may charge account against cgroup which has no tasks.
@@ -2495,7 +2509,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
 
 	id = swap_cgroup_record(ent, 0);
 	rcu_read_lock();
-	memcg = mem_cgroup_lookup(id);
+	memcg = id_to_memcg(id);
 	if (memcg) {
 		/*
 		 * We uncharge this because swap is freed.
@@ -2504,9 +2518,10 @@ void mem_cgroup_uncharge_swap(swp_entry_
 		if (!mem_cgroup_is_root(memcg))
 			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
 		mem_cgroup_swap_statistics(memcg, false);
+		rcu_read_unlock();
 		mem_cgroup_put(memcg);
-	}
-	rcu_read_unlock();
+	} else
+		rcu_read_unlock();
 }
 
 /**
@@ -4010,6 +4025,9 @@ static struct mem_cgroup *mem_cgroup_all
 	struct mem_cgroup *mem;
 	int size = sizeof(struct mem_cgroup);
 
+	if (atomic_read(&mem_cgroup_num) == NR_MEMCG_GROUPS)
+		return NULL;
+
 	/* Can be very big if MAX_NUMNODES is very big */
 	if (size < PAGE_SIZE)
 		mem = kmalloc(size, GFP_KERNEL);
@@ -4020,6 +4038,7 @@ static struct mem_cgroup *mem_cgroup_all
 		return NULL;
 
 	memset(mem, 0, size);
+	mem->valid = 1;
 	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
 	if (!mem->stat) {
 		if (size < PAGE_SIZE)
@@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
 	mem_cgroup_remove_from_trees(mem);
 	free_css_id(&mem_cgroup_subsys, &mem->css);
 
+	atomic_dec(&mem_cgroup_num);
 	for_each_node_state(node, N_POSSIBLE)
 		free_mem_cgroup_per_zone_info(mem, node);
 
@@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
 		vfree(mem);
 }
 
+static void mem_cgroup_free(struct mem_cgroup *mem)
+{
+	/* No more lookup */
+	mem->valid = 0;
+	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
+	/*
+	 * Because we call vfree() etc...use synchronize_rcu() rather than
+ 	 * call_rcu();
+ 	 */
+	synchronize_rcu();
+	__mem_cgroup_free(mem);
+}
+
 static void mem_cgroup_get(struct mem_cgroup *mem)
 {
 	atomic_inc(&mem->refcnt);
@@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
 {
 	if (atomic_sub_and_test(count, &mem->refcnt)) {
 		struct mem_cgroup *parent = parent_mem_cgroup(mem);
-		__mem_cgroup_free(mem);
+		mem_cgroup_free(mem);
 		if (parent)
 			mem_cgroup_put(parent);
 	}
@@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
 	atomic_set(&mem->refcnt, 1);
 	mem->move_charge_at_immigrate = 0;
 	mutex_init(&mem->thresholds_lock);
+	atomic_inc(&mem_cgroup_num);
+	register_memcg_id(mem);
 	return &mem->css;
 free_out:
-	__mem_cgroup_free(mem);
+	mem_cgroup_free(mem);
 	root_mem_cgroup = NULL;
 	return ERR_PTR(error);
 }
Index: mmotm-0811/init/Kconfig
===================================================================
--- mmotm-0811.orig/init/Kconfig
+++ mmotm-0811/init/Kconfig
@@ -594,6 +594,16 @@ config CGROUP_MEM_RES_CTLR_SWAP
 	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 	  size is 4096bytes, 512k per 1Gbytes of swap.
 
+config MEM_CGROUP_MAX_GROUPS
+	int "Maximum number of memory cgroups on a system"
+	range 1 65535
+	default 8192 if 64BIT
+	default 2048 if 32BIT
+	help
+	  Memory cgroup has limitation of the number of groups created.
+	  Please select your favorite value. The more you allow, the more
+	  memory(a pointer per group) will be consumed.
+
 menuconfig CGROUP_SCHED
 	bool "Group CPU scheduler"
 	depends on EXPERIMENTAL && CGROUPS

[PATCH 2/5] memcg: quick memcg lookup array

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Now, memory cgroup has an ID per cgroup and make use of it at
 - hierarchy walk,
 - swap recording.

This patch is for making more use of it. The final purpose is
to replace page_cgroup->mem_cgroup's pointer to an unsigned short.

This patch caches a pointer of memcg in an array. By this, we
don't have to call css_lookup() which requires radix-hash walk.
This saves some amount of memory footprint at lookup memcg via id.

Changelog: 20100825
 - applied comments.

Changelog: 20100811
 - adjusted onto mmotm-2010-08-11
 - fixed RCU related parts.
 - use attach_id() callback.

Changelog: 20100804
 - fixed description in init/Kconfig

Changelog: 20100730
 - fixed rcu_read_unlock() placement.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 init/Kconfig    |   10 +++++++
 mm/memcontrol.c |   75 +++++++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 65 insertions(+), 20 deletions(-)

Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
  */
 struct mem_cgroup {
 	struct cgroup_subsys_state css;
+	int	valid; /* for checking validness under RCU access.*/
 	/*
 	 * the counter to account for memory usage
 	 */
@@ -294,6 +295,29 @@ static bool move_file(void)
 					&mc.to->move_charge_at_immigrate);
 }
 
+/* 0 is unused */
+static atomic_t mem_cgroup_num;
+#define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
+static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
+
+/* Must be called under rcu_read_lock */
+static struct mem_cgroup *id_to_memcg(unsigned short id)
+{
+	struct mem_cgroup *mem;
+	/* see mem_cgroup_free() */
+	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
+	if (likely(mem && mem->valid))
+		return mem;
+	return NULL;
+}
+
+static void register_memcg_id(struct mem_cgroup *mem)
+{
+	int id = css_id(&mem->css);
+	rcu_assign_pointer(mem_cgroups[id], mem);
+	VM_BUG_ON(!mem->valid);
+}
+
 /*
  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
  * limit reclaim to prevent infinite loops, if they ever occur.
@@ -1847,18 +1871,7 @@ static void mem_cgroup_cancel_charge(str
  * it's concern. (dropping refcnt from swap can be called against removed
  * memcg.)
  */
-static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
-{
-	struct cgroup_subsys_state *css;
 
-	/* ID 0 is unused ID */
-	if (!id)
-		return NULL;
-	css = css_lookup(&mem_cgroup_subsys, id);
-	if (!css)
-		return NULL;
-	return container_of(css, struct mem_cgroup, css);
-}
 
 struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
 {
@@ -1879,7 +1892,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr
 		ent.val = page_private(page);
 		id = lookup_swap_cgroup(ent);
 		rcu_read_lock();
-		mem = mem_cgroup_lookup(id);
+		mem = id_to_memcg(id);
 		if (mem && !css_tryget(&mem->css))
 			mem = NULL;
 		rcu_read_unlock();
@@ -2231,7 +2244,7 @@ __mem_cgroup_commit_charge_swapin(struct
 
 		id = swap_cgroup_record(ent, 0);
 		rcu_read_lock();
-		memcg = mem_cgroup_lookup(id);
+		memcg = id_to_memcg(id);
 		if (memcg) {
 			/*
 			 * This recorded memcg can be obsolete one. So, avoid
@@ -2240,9 +2253,10 @@ __mem_cgroup_commit_charge_swapin(struct
 			if (!mem_cgroup_is_root(memcg))
 				res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
 			mem_cgroup_swap_statistics(memcg, false);
+			rcu_read_unlock();
 			mem_cgroup_put(memcg);
-		}
-		rcu_read_unlock();
+		} else
+			rcu_read_unlock();
 	}
 	/*
 	 * At swapin, we may charge account against cgroup which has no tasks.
@@ -2495,7 +2509,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
 
 	id = swap_cgroup_record(ent, 0);
 	rcu_read_lock();
-	memcg = mem_cgroup_lookup(id);
+	memcg = id_to_memcg(id);
 	if (memcg) {
 		/*
 		 * We uncharge this because swap is freed.
@@ -2504,9 +2518,10 @@ void mem_cgroup_uncharge_swap(swp_entry_
 		if (!mem_cgroup_is_root(memcg))
 			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
 		mem_cgroup_swap_statistics(memcg, false);
+		rcu_read_unlock();
 		mem_cgroup_put(memcg);
-	}
-	rcu_read_unlock();
+	} else
+		rcu_read_unlock();
 }
 
 /**
@@ -4010,6 +4025,9 @@ static struct mem_cgroup *mem_cgroup_all
 	struct mem_cgroup *mem;
 	int size = sizeof(struct mem_cgroup);
 
+	if (atomic_read(&mem_cgroup_num) == NR_MEMCG_GROUPS)
+		return NULL;
+
 	/* Can be very big if MAX_NUMNODES is very big */
 	if (size < PAGE_SIZE)
 		mem = kmalloc(size, GFP_KERNEL);
@@ -4020,6 +4038,7 @@ static struct mem_cgroup *mem_cgroup_all
 		return NULL;
 
 	memset(mem, 0, size);
+	mem->valid = 1;
 	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
 	if (!mem->stat) {
 		if (size < PAGE_SIZE)
@@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
 	mem_cgroup_remove_from_trees(mem);
 	free_css_id(&mem_cgroup_subsys, &mem->css);
 
+	atomic_dec(&mem_cgroup_num);
 	for_each_node_state(node, N_POSSIBLE)
 		free_mem_cgroup_per_zone_info(mem, node);
 
@@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
 		vfree(mem);
 }
 
+static void mem_cgroup_free(struct mem_cgroup *mem)
+{
+	/* No more lookup */
+	mem->valid = 0;
+	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
+	/*
+	 * Because we call vfree() etc...use synchronize_rcu() rather than
+ 	 * call_rcu();
+ 	 */
+	synchronize_rcu();
+	__mem_cgroup_free(mem);
+}
+
 static void mem_cgroup_get(struct mem_cgroup *mem)
 {
 	atomic_inc(&mem->refcnt);
@@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
 {
 	if (atomic_sub_and_test(count, &mem->refcnt)) {
 		struct mem_cgroup *parent = parent_mem_cgroup(mem);
-		__mem_cgroup_free(mem);
+		mem_cgroup_free(mem);
 		if (parent)
 			mem_cgroup_put(parent);
 	}
@@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
 	atomic_set(&mem->refcnt, 1);
 	mem->move_charge_at_immigrate = 0;
 	mutex_init(&mem->thresholds_lock);
+	atomic_inc(&mem_cgroup_num);
+	register_memcg_id(mem);
 	return &mem->css;
 free_out:
-	__mem_cgroup_free(mem);
+	mem_cgroup_free(mem);
 	root_mem_cgroup = NULL;
 	return ERR_PTR(error);
 }
Index: mmotm-0811/init/Kconfig
===================================================================
--- mmotm-0811.orig/init/Kconfig
+++ mmotm-0811/init/Kconfig
@@ -594,6 +594,16 @@ config CGROUP_MEM_RES_CTLR_SWAP
 	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 	  size is 4096bytes, 512k per 1Gbytes of swap.
 
+config MEM_CGROUP_MAX_GROUPS
+	int "Maximum number of memory cgroups on a system"
+	range 1 65535
+	default 8192 if 64BIT
+	default 2048 if 32BIT
+	help
+	  Memory cgroup has limitation of the number of groups created.
+	  Please select your favorite value. The more you allow, the more
+	  memory(a pointer per group) will be consumed.
+
 menuconfig CGROUP_SCHED
 	bool "Group CPU scheduler"
 	depends on EXPERIMENTAL && CGROUPS

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[PATCH 3/5] memcg: use ID instead of pointer in page_cgroup

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Now, addresses of memory cgroup can be calculated by their ID without complex.
This patch relplaces pc->mem_cgroup from a pointer to a unsigned short.
On 64bit architecture, this offers us more 6bytes room per page_cgroup.
Use 2bytes for blkio-cgroup's page tracking. More 4bytes will be used for
some light-weight concurrent access.

We may able to move this id onto flags field but ...go step by step.

Changelog: 20100824
 - fixed comments, and typo.
Changelog: 20100811
 - using new rcu APIs, as rcu_dereference_check() etc.
Changelog: 20100804
 - added comments to page_cgroup.h
Changelog: 20100730
 - fixed some garbage added by debug code in early stage

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 include/linux/page_cgroup.h |    6 ++++
 mm/memcontrol.c             |   53 ++++++++++++++++++++++++++++----------------
 mm/page_cgroup.c            |    2 -
 3 files changed, 40 insertions(+), 21 deletions(-)

Index: mmotm-0811/include/linux/page_cgroup.h
===================================================================
--- mmotm-0811.orig/include/linux/page_cgroup.h
+++ mmotm-0811/include/linux/page_cgroup.h
@@ -9,10 +9,14 @@
  * page_cgroup helps us identify information about the cgroup
  * All page cgroups are allocated at boot or memory hotplug event,
  * then the page cgroup for pfn always exists.
+ *
+ * TODO: It seems ID for cgroup can be packed into "flags". But there will
+ * be race between assigning ID <-> set/clear flags. Please be careful.
  */
 struct page_cgroup {
 	unsigned long flags;
-	struct mem_cgroup *mem_cgroup;
+	unsigned short mem_cgroup;	/* ID of assigned memory cgroup */
+	unsigned short blk_cgroup;	/* Not Used..but will be. */
 	struct page *page;
 	struct list_head lru;		/* per cgroup LRU list */
 };
Index: mmotm-0811/mm/page_cgroup.c
===================================================================
--- mmotm-0811.orig/mm/page_cgroup.c
+++ mmotm-0811/mm/page_cgroup.c
@@ -15,7 +15,7 @@ static void __meminit
 __init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
 {
 	pc->flags = 0;
-	pc->mem_cgroup = NULL;
+	pc->mem_cgroup = 0;
 	pc->page = pfn_to_page(pfn);
 	INIT_LIST_HEAD(&pc->lru);
 }
Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -300,12 +300,16 @@ static atomic_t mem_cgroup_num;
 #define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
 static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
 
-/* Must be called under rcu_read_lock */
-static struct mem_cgroup *id_to_memcg(unsigned short id)
+/*
+ * Must be called under rcu_read_lock, Set safe==true if you're sure
+ * you're in safe condition...under lock_page_cgroup() etc.
+ */
+static struct mem_cgroup *id_to_memcg(unsigned short id, bool safe)
 {
 	struct mem_cgroup *mem;
 	/* see mem_cgroup_free() */
-	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
+	mem = rcu_dereference_check(mem_cgroups[id],
+				rcu_read_lock_held() || safe);
 	if (likely(mem && mem->valid))
 		return mem;
 	return NULL;
@@ -381,7 +385,12 @@ struct cgroup_subsys_state *mem_cgroup_c
 static struct mem_cgroup_per_zone *
 page_cgroup_zoneinfo(struct page_cgroup *pc)
 {
-	struct mem_cgroup *mem = pc->mem_cgroup;
+	/*
+	 * The caller should guarantee this "pc" is under lock. In typical
+	 * case, this function is called by lru function with zone->lru_lock.
+	 * It is a safe access.
+	 */
+	struct mem_cgroup *mem = id_to_memcg(pc->mem_cgroup, true);
 	int nid = page_cgroup_nid(pc);
 	int zid = page_cgroup_zid(pc);
 
@@ -723,6 +732,11 @@ static inline bool mem_cgroup_is_root(st
 	return (mem == root_mem_cgroup);
 }
 
+static inline bool mem_cgroup_is_rootid(unsigned short id)
+{
+	return (id == 1);
+}
+
 /*
  * Following LRU functions are allowed to be used without PCG_LOCK.
  * Operations are called by routine of global LRU independently from memcg.
@@ -755,7 +769,7 @@ void mem_cgroup_del_lru_list(struct page
 	 */
 	mz = page_cgroup_zoneinfo(pc);
 	MEM_CGROUP_ZSTAT(mz, lru) -= 1;
-	if (mem_cgroup_is_root(pc->mem_cgroup))
+	if (mem_cgroup_is_rootid(pc->mem_cgroup))
 		return;
 	VM_BUG_ON(list_empty(&pc->lru));
 	list_del_init(&pc->lru);
@@ -782,7 +796,7 @@ void mem_cgroup_rotate_lru_list(struct p
 	 */
 	smp_rmb();
 	/* unused or root page is not rotated. */
-	if (!PageCgroupUsed(pc) || mem_cgroup_is_root(pc->mem_cgroup))
+	if (!PageCgroupUsed(pc) || mem_cgroup_is_rootid(pc->mem_cgroup))
 		return;
 	mz = page_cgroup_zoneinfo(pc);
 	list_move(&pc->lru, &mz->lists[lru]);
@@ -808,7 +822,7 @@ void mem_cgroup_add_lru_list(struct page
 	mz = page_cgroup_zoneinfo(pc);
 	MEM_CGROUP_ZSTAT(mz, lru) += 1;
 	SetPageCgroupAcctLRU(pc);
-	if (mem_cgroup_is_root(pc->mem_cgroup))
+	if (mem_cgroup_is_rootid(pc->mem_cgroup))
 		return;
 	list_add(&pc->lru, &mz->lists[lru]);
 }
@@ -1497,7 +1511,7 @@ void mem_cgroup_update_file_mapped(struc
 		return;
 
 	lock_page_cgroup(pc);
-	mem = pc->mem_cgroup;
+	mem = id_to_memcg(pc->mem_cgroup, true);
 	if (!mem || !PageCgroupUsed(pc))
 		goto done;
 
@@ -1885,14 +1899,14 @@ struct mem_cgroup *try_get_mem_cgroup_fr
 	pc = lookup_page_cgroup(page);
 	lock_page_cgroup(pc);
 	if (PageCgroupUsed(pc)) {
-		mem = pc->mem_cgroup;
+		mem = id_to_memcg(pc->mem_cgroup, true);
 		if (mem && !css_tryget(&mem->css))
 			mem = NULL;
 	} else if (PageSwapCache(page)) {
 		ent.val = page_private(page);
 		id = lookup_swap_cgroup(ent);
 		rcu_read_lock();
-		mem = id_to_memcg(id);
+		mem = id_to_memcg(id, false);
 		if (mem && !css_tryget(&mem->css))
 			mem = NULL;
 		rcu_read_unlock();
@@ -1921,7 +1935,7 @@ static void __mem_cgroup_commit_charge(s
 		return;
 	}
 
-	pc->mem_cgroup = mem;
+	pc->mem_cgroup = css_id(&mem->css);
 	/*
 	 * We access a page_cgroup asynchronously without lock_page_cgroup().
 	 * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
@@ -1979,7 +1993,7 @@ static void __mem_cgroup_move_account(st
 	VM_BUG_ON(PageLRU(pc->page));
 	VM_BUG_ON(!PageCgroupLocked(pc));
 	VM_BUG_ON(!PageCgroupUsed(pc));
-	VM_BUG_ON(pc->mem_cgroup != from);
+	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
 
 	if (PageCgroupFileMapped(pc)) {
 		/* Update mapped_file data for mem_cgroup */
@@ -1994,7 +2008,7 @@ static void __mem_cgroup_move_account(st
 		mem_cgroup_cancel_charge(from);
 
 	/* caller should have done css_get */
-	pc->mem_cgroup = to;
+	pc->mem_cgroup = css_id(&to->css);
 	mem_cgroup_charge_statistics(to, pc, true);
 	/*
 	 * We charges against "to" which may not have any tasks. Then, "to"
@@ -2014,7 +2028,7 @@ static int mem_cgroup_move_account(struc
 {
 	int ret = -EINVAL;
 	lock_page_cgroup(pc);
-	if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
+	if (PageCgroupUsed(pc) && id_to_memcg(pc->mem_cgroup, true) == from) {
 		__mem_cgroup_move_account(pc, from, to, uncharge);
 		ret = 0;
 	}
@@ -2244,7 +2258,7 @@ __mem_cgroup_commit_charge_swapin(struct
 
 		id = swap_cgroup_record(ent, 0);
 		rcu_read_lock();
-		memcg = id_to_memcg(id);
+		memcg = id_to_memcg(id, false);
 		if (memcg) {
 			/*
 			 * This recorded memcg can be obsolete one. So, avoid
@@ -2354,7 +2368,7 @@ __mem_cgroup_uncharge_common(struct page
 
 	lock_page_cgroup(pc);
 
-	mem = pc->mem_cgroup;
+	mem = id_to_memcg(pc->mem_cgroup, true);
 
 	if (!PageCgroupUsed(pc))
 		goto unlock_out;
@@ -2509,7 +2523,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
 
 	id = swap_cgroup_record(ent, 0);
 	rcu_read_lock();
-	memcg = id_to_memcg(id);
+	memcg = id_to_memcg(id, false);
 	if (memcg) {
 		/*
 		 * We uncharge this because swap is freed.
@@ -2600,7 +2614,7 @@ int mem_cgroup_prepare_migration(struct 
 	pc = lookup_page_cgroup(page);
 	lock_page_cgroup(pc);
 	if (PageCgroupUsed(pc)) {
-		mem = pc->mem_cgroup;
+		mem = id_to_memcg(pc->mem_cgroup, true);
 		css_get(&mem->css);
 		/*
 		 * At migrating an anonymous page, its mapcount goes down
@@ -4440,7 +4454,8 @@ static int is_target_pte_for_mc(struct v
 		 * mem_cgroup_move_account() checks the pc is valid or not under
 		 * the lock.
 		 */
-		if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
+		if (PageCgroupUsed(pc) &&
+			id_to_memcg(pc->mem_cgroup, true) == mc.from) {
 			ret = MC_TARGET_PAGE;
 			if (target)
 				target->page = page;

[PATCH 3/5] memcg: use ID instead of pointer in page_cgroup

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Now, addresses of memory cgroup can be calculated by their ID without complex.
This patch relplaces pc->mem_cgroup from a pointer to a unsigned short.
On 64bit architecture, this offers us more 6bytes room per page_cgroup.
Use 2bytes for blkio-cgroup's page tracking. More 4bytes will be used for
some light-weight concurrent access.

We may able to move this id onto flags field but ...go step by step.

Changelog: 20100824
 - fixed comments, and typo.
Changelog: 20100811
 - using new rcu APIs, as rcu_dereference_check() etc.
Changelog: 20100804
 - added comments to page_cgroup.h
Changelog: 20100730
 - fixed some garbage added by debug code in early stage

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 include/linux/page_cgroup.h |    6 ++++
 mm/memcontrol.c             |   53 ++++++++++++++++++++++++++++----------------
 mm/page_cgroup.c            |    2 -
 3 files changed, 40 insertions(+), 21 deletions(-)

Index: mmotm-0811/include/linux/page_cgroup.h
===================================================================
--- mmotm-0811.orig/include/linux/page_cgroup.h
+++ mmotm-0811/include/linux/page_cgroup.h
@@ -9,10 +9,14 @@
  * page_cgroup helps us identify information about the cgroup
  * All page cgroups are allocated at boot or memory hotplug event,
  * then the page cgroup for pfn always exists.
+ *
+ * TODO: It seems ID for cgroup can be packed into "flags". But there will
+ * be race between assigning ID <-> set/clear flags. Please be careful.
  */
 struct page_cgroup {
 	unsigned long flags;
-	struct mem_cgroup *mem_cgroup;
+	unsigned short mem_cgroup;	/* ID of assigned memory cgroup */
+	unsigned short blk_cgroup;	/* Not Used..but will be. */
 	struct page *page;
 	struct list_head lru;		/* per cgroup LRU list */
 };
Index: mmotm-0811/mm/page_cgroup.c
===================================================================
--- mmotm-0811.orig/mm/page_cgroup.c
+++ mmotm-0811/mm/page_cgroup.c
@@ -15,7 +15,7 @@ static void __meminit
 __init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
 {
 	pc->flags = 0;
-	pc->mem_cgroup = NULL;
+	pc->mem_cgroup = 0;
 	pc->page = pfn_to_page(pfn);
 	INIT_LIST_HEAD(&pc->lru);
 }
Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -300,12 +300,16 @@ static atomic_t mem_cgroup_num;
 #define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
 static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
 
-/* Must be called under rcu_read_lock */
-static struct mem_cgroup *id_to_memcg(unsigned short id)
+/*
+ * Must be called under rcu_read_lock, Set safe==true if you're sure
+ * you're in safe condition...under lock_page_cgroup() etc.
+ */
+static struct mem_cgroup *id_to_memcg(unsigned short id, bool safe)
 {
 	struct mem_cgroup *mem;
 	/* see mem_cgroup_free() */
-	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
+	mem = rcu_dereference_check(mem_cgroups[id],
+				rcu_read_lock_held() || safe);
 	if (likely(mem && mem->valid))
 		return mem;
 	return NULL;
@@ -381,7 +385,12 @@ struct cgroup_subsys_state *mem_cgroup_c
 static struct mem_cgroup_per_zone *
 page_cgroup_zoneinfo(struct page_cgroup *pc)
 {
-	struct mem_cgroup *mem = pc->mem_cgroup;
+	/*
+	 * The caller should guarantee this "pc" is under lock. In typical
+	 * case, this function is called by lru function with zone->lru_lock.
+	 * It is a safe access.
+	 */
+	struct mem_cgroup *mem = id_to_memcg(pc->mem_cgroup, true);
 	int nid = page_cgroup_nid(pc);
 	int zid = page_cgroup_zid(pc);
 
@@ -723,6 +732,11 @@ static inline bool mem_cgroup_is_root(st
 	return (mem == root_mem_cgroup);
 }
 
+static inline bool mem_cgroup_is_rootid(unsigned short id)
+{
+	return (id == 1);
+}
+
 /*
  * Following LRU functions are allowed to be used without PCG_LOCK.
  * Operations are called by routine of global LRU independently from memcg.
@@ -755,7 +769,7 @@ void mem_cgroup_del_lru_list(struct page
 	 */
 	mz = page_cgroup_zoneinfo(pc);
 	MEM_CGROUP_ZSTAT(mz, lru) -= 1;
-	if (mem_cgroup_is_root(pc->mem_cgroup))
+	if (mem_cgroup_is_rootid(pc->mem_cgroup))
 		return;
 	VM_BUG_ON(list_empty(&pc->lru));
 	list_del_init(&pc->lru);
@@ -782,7 +796,7 @@ void mem_cgroup_rotate_lru_list(struct p
 	 */
 	smp_rmb();
 	/* unused or root page is not rotated. */
-	if (!PageCgroupUsed(pc) || mem_cgroup_is_root(pc->mem_cgroup))
+	if (!PageCgroupUsed(pc) || mem_cgroup_is_rootid(pc->mem_cgroup))
 		return;
 	mz = page_cgroup_zoneinfo(pc);
 	list_move(&pc->lru, &mz->lists[lru]);
@@ -808,7 +822,7 @@ void mem_cgroup_add_lru_list(struct page
 	mz = page_cgroup_zoneinfo(pc);
 	MEM_CGROUP_ZSTAT(mz, lru) += 1;
 	SetPageCgroupAcctLRU(pc);
-	if (mem_cgroup_is_root(pc->mem_cgroup))
+	if (mem_cgroup_is_rootid(pc->mem_cgroup))
 		return;
 	list_add(&pc->lru, &mz->lists[lru]);
 }
@@ -1497,7 +1511,7 @@ void mem_cgroup_update_file_mapped(struc
 		return;
 
 	lock_page_cgroup(pc);
-	mem = pc->mem_cgroup;
+	mem = id_to_memcg(pc->mem_cgroup, true);
 	if (!mem || !PageCgroupUsed(pc))
 		goto done;
 
@@ -1885,14 +1899,14 @@ struct mem_cgroup *try_get_mem_cgroup_fr
 	pc = lookup_page_cgroup(page);
 	lock_page_cgroup(pc);
 	if (PageCgroupUsed(pc)) {
-		mem = pc->mem_cgroup;
+		mem = id_to_memcg(pc->mem_cgroup, true);
 		if (mem && !css_tryget(&mem->css))
 			mem = NULL;
 	} else if (PageSwapCache(page)) {
 		ent.val = page_private(page);
 		id = lookup_swap_cgroup(ent);
 		rcu_read_lock();
-		mem = id_to_memcg(id);
+		mem = id_to_memcg(id, false);
 		if (mem && !css_tryget(&mem->css))
 			mem = NULL;
 		rcu_read_unlock();
@@ -1921,7 +1935,7 @@ static void __mem_cgroup_commit_charge(s
 		return;
 	}
 
-	pc->mem_cgroup = mem;
+	pc->mem_cgroup = css_id(&mem->css);
 	/*
 	 * We access a page_cgroup asynchronously without lock_page_cgroup().
 	 * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
@@ -1979,7 +1993,7 @@ static void __mem_cgroup_move_account(st
 	VM_BUG_ON(PageLRU(pc->page));
 	VM_BUG_ON(!PageCgroupLocked(pc));
 	VM_BUG_ON(!PageCgroupUsed(pc));
-	VM_BUG_ON(pc->mem_cgroup != from);
+	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
 
 	if (PageCgroupFileMapped(pc)) {
 		/* Update mapped_file data for mem_cgroup */
@@ -1994,7 +2008,7 @@ static void __mem_cgroup_move_account(st
 		mem_cgroup_cancel_charge(from);
 
 	/* caller should have done css_get */
-	pc->mem_cgroup = to;
+	pc->mem_cgroup = css_id(&to->css);
 	mem_cgroup_charge_statistics(to, pc, true);
 	/*
 	 * We charges against "to" which may not have any tasks. Then, "to"
@@ -2014,7 +2028,7 @@ static int mem_cgroup_move_account(struc
 {
 	int ret = -EINVAL;
 	lock_page_cgroup(pc);
-	if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
+	if (PageCgroupUsed(pc) && id_to_memcg(pc->mem_cgroup, true) == from) {
 		__mem_cgroup_move_account(pc, from, to, uncharge);
 		ret = 0;
 	}
@@ -2244,7 +2258,7 @@ __mem_cgroup_commit_charge_swapin(struct
 
 		id = swap_cgroup_record(ent, 0);
 		rcu_read_lock();
-		memcg = id_to_memcg(id);
+		memcg = id_to_memcg(id, false);
 		if (memcg) {
 			/*
 			 * This recorded memcg can be obsolete one. So, avoid
@@ -2354,7 +2368,7 @@ __mem_cgroup_uncharge_common(struct page
 
 	lock_page_cgroup(pc);
 
-	mem = pc->mem_cgroup;
+	mem = id_to_memcg(pc->mem_cgroup, true);
 
 	if (!PageCgroupUsed(pc))
 		goto unlock_out;
@@ -2509,7 +2523,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
 
 	id = swap_cgroup_record(ent, 0);
 	rcu_read_lock();
-	memcg = id_to_memcg(id);
+	memcg = id_to_memcg(id, false);
 	if (memcg) {
 		/*
 		 * We uncharge this because swap is freed.
@@ -2600,7 +2614,7 @@ int mem_cgroup_prepare_migration(struct 
 	pc = lookup_page_cgroup(page);
 	lock_page_cgroup(pc);
 	if (PageCgroupUsed(pc)) {
-		mem = pc->mem_cgroup;
+		mem = id_to_memcg(pc->mem_cgroup, true);
 		css_get(&mem->css);
 		/*
 		 * At migrating an anonymous page, its mapcount goes down
@@ -4440,7 +4454,8 @@ static int is_target_pte_for_mc(struct v
 		 * mem_cgroup_move_account() checks the pc is valid or not under
 		 * the lock.
 		 */
-		if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
+		if (PageCgroupUsed(pc) &&
+			id_to_memcg(pc->mem_cgroup, true) == mc.from) {
 			ret = MC_TARGET_PAGE;
 			if (target)
 				target->page = page;

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[PATCH 4/5] memcg: lockless update of file stat with move-account safe method

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

At accounting file events per memory cgroup, we need to find memory cgroup
via page_cgroup->mem_cgroup. Now, we use lock_page_cgroup().

But, considering the context which page-cgroup for files are accessed,
we can use alternative light-weight mutual execusion in the most case.
At handling file-caches, the only race we have to take care of is "moving"
account, IOW, overwriting page_cgroup->mem_cgroup. Because file status
update is done while the page-cache is in stable state, we don't have to
take care of race with charge/uncharge.

Unlike charge/uncharge, "move" happens not so frequently. It happens only when
rmdir() and task-moving (with a special settings.)
This patch adds a race-checker for file-cache-status accounting v.s. account
moving. The new per-cpu-per-memcg counter MEM_CGROUP_ON_MOVE is added.
The routine for account move 
  1. Increment it before start moving
  2. Call synchronize_rcu()
  3. Decrement it after the end of moving.
By this, file-status-counting routine can check it needs to call
lock_page_cgroup(). In most case, I doesn't need to call it.

Changelog: 20100825
 - added a comment about mc.lock
 - fixed bad lock.
Changelog: 20100804
 - added a comment for possible optimization hint.
Changelog: 20100730
 - some cleanup.
Changelog: 20100729
 - replaced __this_cpu_xxx() with this_cpu_xxx
   (because we don't call spinlock)
 - added VM_BUG_ON().

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 69 insertions(+), 12 deletions(-)

Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -90,6 +90,7 @@ enum mem_cgroup_stat_index {
 	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
 	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
 	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
+	MEM_CGROUP_ON_MOVE,   /* A check for locking move account/status */
 
 	MEM_CGROUP_STAT_NSTATS,
 };
@@ -1089,7 +1090,52 @@ static unsigned int get_swappiness(struc
 	return swappiness;
 }
 
-/* A routine for testing mem is not under move_account */
+static void mem_cgroup_start_move(struct mem_cgroup *mem)
+{
+	int cpu;
+	/*
+	 * reuse mc.lock.
+	 */
+	spin_lock(&mc.lock);
+	/* TODO: Can we optimize this by for_each_online_cpu() ? */
+	for_each_possible_cpu(cpu)
+		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
+	spin_unlock(&mc.lock);
+
+	synchronize_rcu();
+}
+
+static void mem_cgroup_end_move(struct mem_cgroup *mem)
+{
+	int cpu;
+
+	if (!mem)
+		return;
+	/* for fast checking in mem_cgroup_update_file_stat() etc..*/
+	spin_lock(&mc.lock);
+	for_each_possible_cpu(cpu)
+		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) -= 1;
+	spin_unlock(&mc.lock);
+}
+
+/*
+ * mem_cgroup_is_moved -- checking a cgroup is mc.from target or not.
+ *                          used for avoiding race.
+ * mem_cgroup_under_move -- checking a cgroup is mc.from or mc.to or
+ *			    under hierarchy of them. used for waiting at
+ *			    memory pressure.
+ * Result of is_moved can be trusted until the end of rcu_read_unlock().
+ * The caller must do
+ *	rcu_read_lock();
+ *	result = mem_cgroup_is_moved();
+ *	.....make use of result here....
+ *	rcu_read_unlock();
+ */
+static bool mem_cgroup_is_moved(struct mem_cgroup *mem)
+{
+	VM_BUG_ON(!rcu_read_lock_held());
+	return this_cpu_read(mem->stat->count[MEM_CGROUP_ON_MOVE]) > 0;
+}
 
 static bool mem_cgroup_under_move(struct mem_cgroup *mem)
 {
@@ -1505,29 +1551,36 @@ void mem_cgroup_update_file_mapped(struc
 {
 	struct mem_cgroup *mem;
 	struct page_cgroup *pc;
+	bool need_lock = false;
 
 	pc = lookup_page_cgroup(page);
 	if (unlikely(!pc))
 		return;
-
-	lock_page_cgroup(pc);
+	rcu_read_lock();
 	mem = id_to_memcg(pc->mem_cgroup, true);
-	if (!mem || !PageCgroupUsed(pc))
+	if (likely(mem)) {
+		if (mem_cgroup_is_moved(mem)) {
+			/* need to serialize with move_account */
+			lock_page_cgroup(pc);
+			need_lock = true;
+			mem = id_to_memcg(pc->mem_cgroup, true);
+			if (unlikely(!mem))
+				goto done;
+		}
+	}
+	if (unlikely(!PageCgroupUsed(pc)))
 		goto done;
-
-	/*
-	 * Preemption is already disabled. We can use __this_cpu_xxx
-	 */
 	if (val > 0) {
-		__this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+		this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
 		SetPageCgroupFileMapped(pc);
 	} else {
-		__this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+		this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
 		ClearPageCgroupFileMapped(pc);
 	}
-
 done:
-	unlock_page_cgroup(pc);
+	if (need_lock)
+		unlock_page_cgroup(pc);
+	rcu_read_unlock();
 }
 
 /*
@@ -3067,6 +3120,7 @@ move_account:
 		lru_add_drain_all();
 		drain_all_stock_sync();
 		ret = 0;
+		mem_cgroup_start_move(mem);
 		for_each_node_state(node, N_HIGH_MEMORY) {
 			for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
 				enum lru_list l;
@@ -3080,6 +3134,7 @@ move_account:
 			if (ret)
 				break;
 		}
+		mem_cgroup_end_move(mem);
 		memcg_oom_recover(mem);
 		/* it seems parent cgroup doesn't have enough mem */
 		if (ret == -ENOMEM)
@@ -4564,6 +4619,7 @@ static void mem_cgroup_clear_mc(void)
 	mc.to = NULL;
 	mc.moving_task = NULL;
 	spin_unlock(&mc.lock);
+	mem_cgroup_end_move(from);
 	memcg_oom_recover(from);
 	memcg_oom_recover(to);
 	wake_up_all(&mc.waitq);
@@ -4594,6 +4650,7 @@ static int mem_cgroup_can_attach(struct 
 			VM_BUG_ON(mc.moved_charge);
 			VM_BUG_ON(mc.moved_swap);
 			VM_BUG_ON(mc.moving_task);
+			mem_cgroup_start_move(from);
 			spin_lock(&mc.lock);
 			mc.from = from;
 			mc.to = mem;

[PATCH 4/5] memcg: lockless update of file stat with move-account safe method

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

At accounting file events per memory cgroup, we need to find memory cgroup
via page_cgroup->mem_cgroup. Now, we use lock_page_cgroup().

But, considering the context which page-cgroup for files are accessed,
we can use alternative light-weight mutual execusion in the most case.
At handling file-caches, the only race we have to take care of is "moving"
account, IOW, overwriting page_cgroup->mem_cgroup. Because file status
update is done while the page-cache is in stable state, we don't have to
take care of race with charge/uncharge.

Unlike charge/uncharge, "move" happens not so frequently. It happens only when
rmdir() and task-moving (with a special settings.)
This patch adds a race-checker for file-cache-status accounting v.s. account
moving. The new per-cpu-per-memcg counter MEM_CGROUP_ON_MOVE is added.
The routine for account move 
  1. Increment it before start moving
  2. Call synchronize_rcu()
  3. Decrement it after the end of moving.
By this, file-status-counting routine can check it needs to call
lock_page_cgroup(). In most case, I doesn't need to call it.

Changelog: 20100825
 - added a comment about mc.lock
 - fixed bad lock.
Changelog: 20100804
 - added a comment for possible optimization hint.
Changelog: 20100730
 - some cleanup.
Changelog: 20100729
 - replaced __this_cpu_xxx() with this_cpu_xxx
   (because we don't call spinlock)
 - added VM_BUG_ON().

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 69 insertions(+), 12 deletions(-)

Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -90,6 +90,7 @@ enum mem_cgroup_stat_index {
 	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
 	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
 	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
+	MEM_CGROUP_ON_MOVE,   /* A check for locking move account/status */
 
 	MEM_CGROUP_STAT_NSTATS,
 };
@@ -1089,7 +1090,52 @@ static unsigned int get_swappiness(struc
 	return swappiness;
 }
 
-/* A routine for testing mem is not under move_account */
+static void mem_cgroup_start_move(struct mem_cgroup *mem)
+{
+	int cpu;
+	/*
+	 * reuse mc.lock.
+	 */
+	spin_lock(&mc.lock);
+	/* TODO: Can we optimize this by for_each_online_cpu() ? */
+	for_each_possible_cpu(cpu)
+		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
+	spin_unlock(&mc.lock);
+
+	synchronize_rcu();
+}
+
+static void mem_cgroup_end_move(struct mem_cgroup *mem)
+{
+	int cpu;
+
+	if (!mem)
+		return;
+	/* for fast checking in mem_cgroup_update_file_stat() etc..*/
+	spin_lock(&mc.lock);
+	for_each_possible_cpu(cpu)
+		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) -= 1;
+	spin_unlock(&mc.lock);
+}
+
+/*
+ * mem_cgroup_is_moved -- checking a cgroup is mc.from target or not.
+ *                          used for avoiding race.
+ * mem_cgroup_under_move -- checking a cgroup is mc.from or mc.to or
+ *			    under hierarchy of them. used for waiting at
+ *			    memory pressure.
+ * Result of is_moved can be trusted until the end of rcu_read_unlock().
+ * The caller must do
+ *	rcu_read_lock();
+ *	result = mem_cgroup_is_moved();
+ *	.....make use of result here....
+ *	rcu_read_unlock();
+ */
+static bool mem_cgroup_is_moved(struct mem_cgroup *mem)
+{
+	VM_BUG_ON(!rcu_read_lock_held());
+	return this_cpu_read(mem->stat->count[MEM_CGROUP_ON_MOVE]) > 0;
+}
 
 static bool mem_cgroup_under_move(struct mem_cgroup *mem)
 {
@@ -1505,29 +1551,36 @@ void mem_cgroup_update_file_mapped(struc
 {
 	struct mem_cgroup *mem;
 	struct page_cgroup *pc;
+	bool need_lock = false;
 
 	pc = lookup_page_cgroup(page);
 	if (unlikely(!pc))
 		return;
-
-	lock_page_cgroup(pc);
+	rcu_read_lock();
 	mem = id_to_memcg(pc->mem_cgroup, true);
-	if (!mem || !PageCgroupUsed(pc))
+	if (likely(mem)) {
+		if (mem_cgroup_is_moved(mem)) {
+			/* need to serialize with move_account */
+			lock_page_cgroup(pc);
+			need_lock = true;
+			mem = id_to_memcg(pc->mem_cgroup, true);
+			if (unlikely(!mem))
+				goto done;
+		}
+	}
+	if (unlikely(!PageCgroupUsed(pc)))
 		goto done;
-
-	/*
-	 * Preemption is already disabled. We can use __this_cpu_xxx
-	 */
 	if (val > 0) {
-		__this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+		this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
 		SetPageCgroupFileMapped(pc);
 	} else {
-		__this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+		this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
 		ClearPageCgroupFileMapped(pc);
 	}
-
 done:
-	unlock_page_cgroup(pc);
+	if (need_lock)
+		unlock_page_cgroup(pc);
+	rcu_read_unlock();
 }
 
 /*
@@ -3067,6 +3120,7 @@ move_account:
 		lru_add_drain_all();
 		drain_all_stock_sync();
 		ret = 0;
+		mem_cgroup_start_move(mem);
 		for_each_node_state(node, N_HIGH_MEMORY) {
 			for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
 				enum lru_list l;
@@ -3080,6 +3134,7 @@ move_account:
 			if (ret)
 				break;
 		}
+		mem_cgroup_end_move(mem);
 		memcg_oom_recover(mem);
 		/* it seems parent cgroup doesn't have enough mem */
 		if (ret == -ENOMEM)
@@ -4564,6 +4619,7 @@ static void mem_cgroup_clear_mc(void)
 	mc.to = NULL;
 	mc.moving_task = NULL;
 	spin_unlock(&mc.lock);
+	mem_cgroup_end_move(from);
 	memcg_oom_recover(from);
 	memcg_oom_recover(to);
 	wake_up_all(&mc.waitq);
@@ -4594,6 +4650,7 @@ static int mem_cgroup_can_attach(struct 
 			VM_BUG_ON(mc.moved_charge);
 			VM_BUG_ON(mc.moved_swap);
 			VM_BUG_ON(mc.moving_task);
+			mem_cgroup_start_move(from);
 			spin_lock(&mc.lock);
 			mc.from = from;
 			mc.to = mem;

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[PATCH 5/5] memcg: generic file stat accounting interface

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Preparing for adding new status arounf file caches.(dirty, writeback,etc..)
Using a unified macro and more generic names.
All counters will have the same rule for updating.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 include/linux/memcontrol.h  |   24 ++++++++++++++++++++++
 include/linux/page_cgroup.h |   19 ++++++++++++------
 mm/memcontrol.c             |   46 ++++++++++++++++++--------------------------
 3 files changed, 56 insertions(+), 33 deletions(-)

Index: mmotm-0811/include/linux/memcontrol.h
===================================================================
--- mmotm-0811.orig/include/linux/memcontrol.h
+++ mmotm-0811/include/linux/memcontrol.h
@@ -25,6 +25,30 @@ struct page_cgroup;
 struct page;
 struct mm_struct;
 
+/*
+ * Per-cpu Statistics for memory cgroup.
+ */
+enum mem_cgroup_stat_index {
+	/*
+	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
+	 */
+	MEM_CGROUP_STAT_CACHE,		/* # of pages charged as cache */
+	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
+	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
+	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
+	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
+	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
+	MEM_CGROUP_ON_MOVE,   /* A check for locking move account/status */
+	/* When you add new member for file-stat, please update page_cgroup.h */
+	MEM_CGROUP_FSTAT_BASE,
+	MEM_CGROUP_FSTAT_FILE_MAPPED = MEM_CGROUP_FSTAT_BASE,
+	MEM_CGROUP_FSTAT_END,
+	MEM_CGROUP_STAT_NSTATS = MEM_CGROUP_FSTAT_END,
+};
+
+#define MEMCG_FSTAT_IDX(idx)	((idx) - MEM_CGROUP_FSTAT_BASE)
+#define NR_FILE_FLAGS_MEMCG ((MEM_CGROUP_FSTAT_END - MEM_CGROUP_FSTAT_BASE))
+
 extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
 					struct list_head *dst,
 					unsigned long *scanned, int order,
Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -76,24 +76,6 @@ static int really_do_swap_account __init
 #define THRESHOLDS_EVENTS_THRESH (7) /* once in 128 */
 #define SOFTLIMIT_EVENTS_THRESH (10) /* once in 1024 */
 
-/*
- * Statistics for memory cgroup.
- */
-enum mem_cgroup_stat_index {
-	/*
-	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
-	 */
-	MEM_CGROUP_STAT_CACHE, 	   /* # of pages charged as cache */
-	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
-	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
-	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
-	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
-	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
-	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
-	MEM_CGROUP_ON_MOVE,   /* A check for locking move account/status */
-
-	MEM_CGROUP_STAT_NSTATS,
-};
 
 struct mem_cgroup_stat_cpu {
 	s64 count[MEM_CGROUP_STAT_NSTATS];
@@ -1547,7 +1529,8 @@ bool mem_cgroup_handle_oom(struct mem_cg
  * Currently used to update mapped file statistics, but the routine can be
  * generalized to update other statistics as well.
  */
-void mem_cgroup_update_file_mapped(struct page *page, int val)
+static void
+mem_cgroup_update_file_stat(struct page *page, unsigned int idx, int val)
 {
 	struct mem_cgroup *mem;
 	struct page_cgroup *pc;
@@ -1571,11 +1554,11 @@ void mem_cgroup_update_file_mapped(struc
 	if (unlikely(!PageCgroupUsed(pc)))
 		goto done;
 	if (val > 0) {
-		this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		SetPageCgroupFileMapped(pc);
+		this_cpu_inc(mem->stat->count[idx]);
+		set_bit(fflag_idx(MEMCG_FSTAT_IDX(idx)), &pc->flags);
 	} else {
-		this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		ClearPageCgroupFileMapped(pc);
+		this_cpu_dec(mem->stat->count[idx]);
+		clear_bit(fflag_idx(MEMCG_FSTAT_IDX(idx)), &pc->flags);
 	}
 done:
 	if (need_lock)
@@ -1583,6 +1566,12 @@ done:
 	rcu_read_unlock();
 }
 
+void mem_cgroup_update_file_mapped(struct page *page, int val)
+{
+	return mem_cgroup_update_file_stat(page,
+		MEM_CGROUP_FSTAT_FILE_MAPPED, val);
+}
+
 /*
  * size of first charge trial. "32" comes from vmscan.c's magic value.
  * TODO: maybe necessary to use big numbers in big irons.
@@ -2042,17 +2031,20 @@ static void __mem_cgroup_commit_charge(s
 static void __mem_cgroup_move_account(struct page_cgroup *pc,
 	struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
 {
+	int i;
 	VM_BUG_ON(from == to);
 	VM_BUG_ON(PageLRU(pc->page));
 	VM_BUG_ON(!PageCgroupLocked(pc));
 	VM_BUG_ON(!PageCgroupUsed(pc));
 	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
 
-	if (PageCgroupFileMapped(pc)) {
+	for (i = MEM_CGROUP_FSTAT_BASE; i < MEM_CGROUP_FSTAT_END; ++i) {
+		if (!test_bit(fflag_idx(MEMCG_FSTAT_IDX(i)), &pc->flags))
+			continue;
 		/* Update mapped_file data for mem_cgroup */
 		preempt_disable();
-		__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+		__this_cpu_dec(from->stat->count[i]);
+		__this_cpu_inc(to->stat->count[i]);
 		preempt_enable();
 	}
 	mem_cgroup_charge_statistics(from, pc, false);
@@ -3483,7 +3475,7 @@ static int mem_cgroup_get_local_stat(str
 	s->stat[MCS_CACHE] += val * PAGE_SIZE;
 	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
 	s->stat[MCS_RSS] += val * PAGE_SIZE;
-	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_MAPPED);
+	val = mem_cgroup_read_stat(mem, MEM_CGROUP_FSTAT_FILE_MAPPED);
 	s->stat[MCS_FILE_MAPPED] += val * PAGE_SIZE;
 	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_PGPGIN_COUNT);
 	s->stat[MCS_PGPGIN] += val;
Index: mmotm-0811/include/linux/page_cgroup.h
===================================================================
--- mmotm-0811.orig/include/linux/page_cgroup.h
+++ mmotm-0811/include/linux/page_cgroup.h
@@ -3,6 +3,7 @@
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 #include <linux/bit_spinlock.h>
+#include <linux/memcontrol.h> /* for flags */
 /*
  * Page Cgroup can be considered as an extended mem_map.
  * A page_cgroup page is associated with every page descriptor. The
@@ -43,10 +44,22 @@ enum {
 	PCG_CACHE, /* charged as cache */
 	PCG_USED, /* this object is in use. */
 	PCG_ACCT_LRU, /* page has been accounted for */
-	PCG_FILE_MAPPED, /* page is accounted as "mapped" */
 	PCG_MIGRATION, /* under page migration */
+	PCG_FILE_FLAGS_MEMCG, /* see memcontrol.h */
+	PCG_FILE_FLAGS_MEMCG_END
+		= PCG_FILE_FLAGS_MEMCG + NR_FILE_FLAGS_MEMCG - 1,
 };
 
+/*
+ * file-stat flags are defined regarding to memcg's stat information.
+ * Here, just defines a macro for indexing
+ */
+static inline int fflag_idx(int idx)
+{
+	VM_BUG_ON((idx) >= NR_FILE_FLAGS_MEMCG);
+	return (idx) + PCG_FILE_FLAGS_MEMCG;
+}
+
 #define TESTPCGFLAG(uname, lname)			\
 static inline int PageCgroup##uname(struct page_cgroup *pc)	\
 	{ return test_bit(PCG_##lname, &pc->flags); }
@@ -79,11 +92,6 @@ CLEARPCGFLAG(AcctLRU, ACCT_LRU)
 TESTPCGFLAG(AcctLRU, ACCT_LRU)
 TESTCLEARPCGFLAG(AcctLRU, ACCT_LRU)
 
-
-SETPCGFLAG(FileMapped, FILE_MAPPED)
-CLEARPCGFLAG(FileMapped, FILE_MAPPED)
-TESTPCGFLAG(FileMapped, FILE_MAPPED)
-
 SETPCGFLAG(Migration, MIGRATION)
 CLEARPCGFLAG(Migration, MIGRATION)
 TESTPCGFLAG(Migration, MIGRATION)

[PATCH 5/5] memcg: generic file stat accounting interface

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Preparing for adding new status arounf file caches.(dirty, writeback,etc..)
Using a unified macro and more generic names.
All counters will have the same rule for updating.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 include/linux/memcontrol.h  |   24 ++++++++++++++++++++++
 include/linux/page_cgroup.h |   19 ++++++++++++------
 mm/memcontrol.c             |   46 ++++++++++++++++++--------------------------
 3 files changed, 56 insertions(+), 33 deletions(-)

Index: mmotm-0811/include/linux/memcontrol.h
===================================================================
--- mmotm-0811.orig/include/linux/memcontrol.h
+++ mmotm-0811/include/linux/memcontrol.h
@@ -25,6 +25,30 @@ struct page_cgroup;
 struct page;
 struct mm_struct;
 
+/*
+ * Per-cpu Statistics for memory cgroup.
+ */
+enum mem_cgroup_stat_index {
+	/*
+	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
+	 */
+	MEM_CGROUP_STAT_CACHE,		/* # of pages charged as cache */
+	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
+	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
+	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
+	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
+	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
+	MEM_CGROUP_ON_MOVE,   /* A check for locking move account/status */
+	/* When you add new member for file-stat, please update page_cgroup.h */
+	MEM_CGROUP_FSTAT_BASE,
+	MEM_CGROUP_FSTAT_FILE_MAPPED = MEM_CGROUP_FSTAT_BASE,
+	MEM_CGROUP_FSTAT_END,
+	MEM_CGROUP_STAT_NSTATS = MEM_CGROUP_FSTAT_END,
+};
+
+#define MEMCG_FSTAT_IDX(idx)	((idx) - MEM_CGROUP_FSTAT_BASE)
+#define NR_FILE_FLAGS_MEMCG ((MEM_CGROUP_FSTAT_END - MEM_CGROUP_FSTAT_BASE))
+
 extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
 					struct list_head *dst,
 					unsigned long *scanned, int order,
Index: mmotm-0811/mm/memcontrol.c
===================================================================
--- mmotm-0811.orig/mm/memcontrol.c
+++ mmotm-0811/mm/memcontrol.c
@@ -76,24 +76,6 @@ static int really_do_swap_account __init
 #define THRESHOLDS_EVENTS_THRESH (7) /* once in 128 */
 #define SOFTLIMIT_EVENTS_THRESH (10) /* once in 1024 */
 
-/*
- * Statistics for memory cgroup.
- */
-enum mem_cgroup_stat_index {
-	/*
-	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
-	 */
-	MEM_CGROUP_STAT_CACHE, 	   /* # of pages charged as cache */
-	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
-	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
-	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
-	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
-	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
-	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
-	MEM_CGROUP_ON_MOVE,   /* A check for locking move account/status */
-
-	MEM_CGROUP_STAT_NSTATS,
-};
 
 struct mem_cgroup_stat_cpu {
 	s64 count[MEM_CGROUP_STAT_NSTATS];
@@ -1547,7 +1529,8 @@ bool mem_cgroup_handle_oom(struct mem_cg
  * Currently used to update mapped file statistics, but the routine can be
  * generalized to update other statistics as well.
  */
-void mem_cgroup_update_file_mapped(struct page *page, int val)
+static void
+mem_cgroup_update_file_stat(struct page *page, unsigned int idx, int val)
 {
 	struct mem_cgroup *mem;
 	struct page_cgroup *pc;
@@ -1571,11 +1554,11 @@ void mem_cgroup_update_file_mapped(struc
 	if (unlikely(!PageCgroupUsed(pc)))
 		goto done;
 	if (val > 0) {
-		this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		SetPageCgroupFileMapped(pc);
+		this_cpu_inc(mem->stat->count[idx]);
+		set_bit(fflag_idx(MEMCG_FSTAT_IDX(idx)), &pc->flags);
 	} else {
-		this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		ClearPageCgroupFileMapped(pc);
+		this_cpu_dec(mem->stat->count[idx]);
+		clear_bit(fflag_idx(MEMCG_FSTAT_IDX(idx)), &pc->flags);
 	}
 done:
 	if (need_lock)
@@ -1583,6 +1566,12 @@ done:
 	rcu_read_unlock();
 }
 
+void mem_cgroup_update_file_mapped(struct page *page, int val)
+{
+	return mem_cgroup_update_file_stat(page,
+		MEM_CGROUP_FSTAT_FILE_MAPPED, val);
+}
+
 /*
  * size of first charge trial. "32" comes from vmscan.c's magic value.
  * TODO: maybe necessary to use big numbers in big irons.
@@ -2042,17 +2031,20 @@ static void __mem_cgroup_commit_charge(s
 static void __mem_cgroup_move_account(struct page_cgroup *pc,
 	struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
 {
+	int i;
 	VM_BUG_ON(from == to);
 	VM_BUG_ON(PageLRU(pc->page));
 	VM_BUG_ON(!PageCgroupLocked(pc));
 	VM_BUG_ON(!PageCgroupUsed(pc));
 	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
 
-	if (PageCgroupFileMapped(pc)) {
+	for (i = MEM_CGROUP_FSTAT_BASE; i < MEM_CGROUP_FSTAT_END; ++i) {
+		if (!test_bit(fflag_idx(MEMCG_FSTAT_IDX(i)), &pc->flags))
+			continue;
 		/* Update mapped_file data for mem_cgroup */
 		preempt_disable();
-		__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+		__this_cpu_dec(from->stat->count[i]);
+		__this_cpu_inc(to->stat->count[i]);
 		preempt_enable();
 	}
 	mem_cgroup_charge_statistics(from, pc, false);
@@ -3483,7 +3475,7 @@ static int mem_cgroup_get_local_stat(str
 	s->stat[MCS_CACHE] += val * PAGE_SIZE;
 	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
 	s->stat[MCS_RSS] += val * PAGE_SIZE;
-	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_MAPPED);
+	val = mem_cgroup_read_stat(mem, MEM_CGROUP_FSTAT_FILE_MAPPED);
 	s->stat[MCS_FILE_MAPPED] += val * PAGE_SIZE;
 	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_PGPGIN_COUNT);
 	s->stat[MCS_PGPGIN] += val;
Index: mmotm-0811/include/linux/page_cgroup.h
===================================================================
--- mmotm-0811.orig/include/linux/page_cgroup.h
+++ mmotm-0811/include/linux/page_cgroup.h
@@ -3,6 +3,7 @@
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 #include <linux/bit_spinlock.h>
+#include <linux/memcontrol.h> /* for flags */
 /*
  * Page Cgroup can be considered as an extended mem_map.
  * A page_cgroup page is associated with every page descriptor. The
@@ -43,10 +44,22 @@ enum {
 	PCG_CACHE, /* charged as cache */
 	PCG_USED, /* this object is in use. */
 	PCG_ACCT_LRU, /* page has been accounted for */
-	PCG_FILE_MAPPED, /* page is accounted as "mapped" */
 	PCG_MIGRATION, /* under page migration */
+	PCG_FILE_FLAGS_MEMCG, /* see memcontrol.h */
+	PCG_FILE_FLAGS_MEMCG_END
+		= PCG_FILE_FLAGS_MEMCG + NR_FILE_FLAGS_MEMCG - 1,
 };
 
+/*
+ * file-stat flags are defined regarding to memcg's stat information.
+ * Here, just defines a macro for indexing
+ */
+static inline int fflag_idx(int idx)
+{
+	VM_BUG_ON((idx) >= NR_FILE_FLAGS_MEMCG);
+	return (idx) + PCG_FILE_FLAGS_MEMCG;
+}
+
 #define TESTPCGFLAG(uname, lname)			\
 static inline int PageCgroup##uname(struct page_cgroup *pc)	\
 	{ return test_bit(PCG_##lname, &pc->flags); }
@@ -79,11 +92,6 @@ CLEARPCGFLAG(AcctLRU, ACCT_LRU)
 TESTPCGFLAG(AcctLRU, ACCT_LRU)
 TESTCLEARPCGFLAG(AcctLRU, ACCT_LRU)
 
-
-SETPCGFLAG(FileMapped, FILE_MAPPED)
-CLEARPCGFLAG(FileMapped, FILE_MAPPED)
-TESTPCGFLAG(FileMapped, FILE_MAPPED)
-
 SETPCGFLAG(Migration, MIGRATION)
 CLEARPCGFLAG(Migration, MIGRATION)
 TESTPCGFLAG(Migration, MIGRATION)

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Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:06:40]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, css'id is allocated after ->create() is called. But to make use of ID
> in ->create(), it should be available before ->create().
> 
> In another thinking, considering the ID is tightly coupled with "css",
> it should be allocated when "css" is allocated.
> This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> memory and blkio are useing ID. (To support complicated hierarchy walk.)
                       ^^^^ typo
> 
> ID will be used in mem cgroup's ->create(), later.
> 
> Note:
> If someone changes rules of css allocation, ID allocation should be moved too.
> 

What rules? could you please elaborate?

Seems cleaner, may be we need to update cgroups.txt?

-- 
	Three Cheers,
	Balbir

Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:06:40]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, css'id is allocated after ->create() is called. But to make use of ID
> in ->create(), it should be available before ->create().
> 
> In another thinking, considering the ID is tightly coupled with "css",
> it should be allocated when "css" is allocated.
> This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> memory and blkio are useing ID. (To support complicated hierarchy walk.)
                       ^^^^ typo
> 
> ID will be used in mem cgroup's ->create(), later.
> 
> Note:
> If someone changes rules of css allocation, ID allocation should be moved too.
> 

What rules? could you please elaborate?

Seems cleaner, may be we need to update cgroups.txt?

-- 
	Three Cheers,
	Balbir

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Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[KAMEZAWA Hiroyuki]

On Wed, 25 Aug 2010 19:45:00 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:06:40]:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > Now, css'id is allocated after ->create() is called. But to make use of ID
> > in ->create(), it should be available before ->create().
> > 
> > In another thinking, considering the ID is tightly coupled with "css",
> > it should be allocated when "css" is allocated.
> > This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> > memory and blkio are useing ID. (To support complicated hierarchy walk.)
>                        ^^^^ typo
> > 
> > ID will be used in mem cgroup's ->create(), later.
> > 
> > Note:
> > If someone changes rules of css allocation, ID allocation should be moved too.
> > 
> 
> What rules? could you please elaborate?
> 
See Paul Menage's mail. He said "allocating css object under kernel/cgroup.c
will make kernel/cgroup.c cleaner." But it seems too big for my purpose.

> Seems cleaner, may be we need to update cgroups.txt?

Hmm. will look into.

Thanks,
-Kame

> 
> -- 
> 	Three Cheers,
> 	Balbir
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
> 
> 

Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[KAMEZAWA Hiroyuki]

On Wed, 25 Aug 2010 19:45:00 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:06:40]:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > Now, css'id is allocated after ->create() is called. But to make use of ID
> > in ->create(), it should be available before ->create().
> > 
> > In another thinking, considering the ID is tightly coupled with "css",
> > it should be allocated when "css" is allocated.
> > This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> > memory and blkio are useing ID. (To support complicated hierarchy walk.)
>                        ^^^^ typo
> > 
> > ID will be used in mem cgroup's ->create(), later.
> > 
> > Note:
> > If someone changes rules of css allocation, ID allocation should be moved too.
> > 
> 
> What rules? could you please elaborate?
> 
See Paul Menage's mail. He said "allocating css object under kernel/cgroup.c
will make kernel/cgroup.c cleaner." But it seems too big for my purpose.

> Seems cleaner, may be we need to update cgroups.txt?

Hmm. will look into.

Thanks,
-Kame

> 
> -- 
> 	Three Cheers,
> 	Balbir
> 
> --
> 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/ .
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> 
> 

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Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:06:40 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, css'id is allocated after ->create() is called. But to make use of ID
> in ->create(), it should be available before ->create().
> 
> In another thinking, considering the ID is tightly coupled with "css",
> it should be allocated when "css" is allocated.
> This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> memory and blkio are useing ID. (To support complicated hierarchy walk.)
> 
> ID will be used in mem cgroup's ->create(), later.
> 
> Note:
> If someone changes rules of css allocation, ID allocation should be moved too.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
I think we need some signs from Paul and Li, but anyway

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Thanks,
Daisuke Nishimura.

> ---
>  block/blk-cgroup.c     |    9 ++++++++
>  include/linux/cgroup.h |   16 ++++++++-------
>  kernel/cgroup.c        |   50 ++++++++++++++-----------------------------------
>  mm/memcontrol.c        |    5 ++++
>  4 files changed, 38 insertions(+), 42 deletions(-)
> 
> Index: mmotm-0811/kernel/cgroup.c
> ===================================================================
> --- mmotm-0811.orig/kernel/cgroup.c
> +++ mmotm-0811/kernel/cgroup.c
> @@ -289,9 +289,6 @@ struct cg_cgroup_link {
>  static struct css_set init_css_set;
>  static struct cg_cgroup_link init_css_set_link;
>  
> -static int cgroup_init_idr(struct cgroup_subsys *ss,
> -			   struct cgroup_subsys_state *css);
> -
>  /* css_set_lock protects the list of css_set objects, and the
>   * chain of tasks off each css_set.  Nests outside task->alloc_lock
>   * due to cgroup_iter_start() */
> @@ -770,9 +767,6 @@ static struct backing_dev_info cgroup_ba
>  	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
>  };
>  
> -static int alloc_css_id(struct cgroup_subsys *ss,
> -			struct cgroup *parent, struct cgroup *child);
> -
>  static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
>  {
>  	struct inode *inode = new_inode(sb);
> @@ -3257,7 +3251,8 @@ static void init_cgroup_css(struct cgrou
>  	css->cgroup = cgrp;
>  	atomic_set(&css->refcnt, 1);
>  	css->flags = 0;
> -	css->id = NULL;
> +	if (!ss->use_id)
> +		css->id = NULL;
>  	if (cgrp == dummytop)
>  		set_bit(CSS_ROOT, &css->flags);
>  	BUG_ON(cgrp->subsys[ss->subsys_id]);
> @@ -3342,12 +3337,6 @@ static long cgroup_create(struct cgroup 
>  			goto err_destroy;
>  		}
>  		init_cgroup_css(css, ss, cgrp);
> -		if (ss->use_id) {
> -			err = alloc_css_id(ss, parent, cgrp);
> -			if (err)
> -				goto err_destroy;
> -		}
> -		/* At error, ->destroy() callback has to free assigned ID. */
>  	}
>  
>  	cgroup_lock_hierarchy(root);
> @@ -3709,17 +3698,6 @@ int __init_or_module cgroup_load_subsys(
>  
>  	/* our new subsystem will be attached to the dummy hierarchy. */
>  	init_cgroup_css(css, ss, dummytop);
> -	/* init_idr must be after init_cgroup_css because it sets css->id. */
> -	if (ss->use_id) {
> -		int ret = cgroup_init_idr(ss, css);
> -		if (ret) {
> -			dummytop->subsys[ss->subsys_id] = NULL;
> -			ss->destroy(ss, dummytop);
> -			subsys[i] = NULL;
> -			mutex_unlock(&cgroup_mutex);
> -			return ret;
> -		}
> -	}
>  
>  	/*
>  	 * Now we need to entangle the css into the existing css_sets. unlike
> @@ -3888,8 +3866,6 @@ int __init cgroup_init(void)
>  		struct cgroup_subsys *ss = subsys[i];
>  		if (!ss->early_init)
>  			cgroup_init_subsys(ss);
> -		if (ss->use_id)
> -			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
>  	}
>  
>  	/* Add init_css_set to the hash table */
> @@ -4603,8 +4579,8 @@ err_out:
>  
>  }
>  
> -static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
> -					    struct cgroup_subsys_state *rootcss)
> +static int cgroup_init_idr(struct cgroup_subsys *ss,
> +			    struct cgroup_subsys_state *rootcss)
>  {
>  	struct css_id *newid;
>  
> @@ -4616,21 +4592,25 @@ static int __init_or_module cgroup_init_
>  		return PTR_ERR(newid);
>  
>  	newid->stack[0] = newid->id;
> -	newid->css = rootcss;
> -	rootcss->id = newid;
> +	rcu_assign_pointer(newid->css, rootcss);
> +	rcu_assign_pointer(rootcss->id, newid);
>  	return 0;
>  }
>  
> -static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
> -			struct cgroup *child)
> +int alloc_css_id(struct cgroup_subsys *ss,
> +	struct cgroup *cgrp, struct cgroup_subsys_state *css)
>  {
>  	int subsys_id, i, depth = 0;
> -	struct cgroup_subsys_state *parent_css, *child_css;
> +	struct cgroup_subsys_state *parent_css;
> +	struct cgroup *parent;
>  	struct css_id *child_id, *parent_id;
>  
> +	if (cgrp == dummytop)
> +		return cgroup_init_idr(ss, css);
> +
> +	parent = cgrp->parent;
>  	subsys_id = ss->subsys_id;
>  	parent_css = parent->subsys[subsys_id];
> -	child_css = child->subsys[subsys_id];
>  	parent_id = parent_css->id;
>  	depth = parent_id->depth + 1;
>  
> @@ -4645,7 +4625,7 @@ static int alloc_css_id(struct cgroup_su
>  	 * child_id->css pointer will be set after this cgroup is available
>  	 * see cgroup_populate_dir()
>  	 */
> -	rcu_assign_pointer(child_css->id, child_id);
> +	rcu_assign_pointer(css->id, child_id);
>  
>  	return 0;
>  }
> Index: mmotm-0811/include/linux/cgroup.h
> ===================================================================
> --- mmotm-0811.orig/include/linux/cgroup.h
> +++ mmotm-0811/include/linux/cgroup.h
> @@ -583,9 +583,11 @@ int cgroup_attach_task_current_cg(struct
>  /*
>   * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
>   * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
> - * CSS ID is assigned at cgroup allocation (create) automatically
> - * and removed when subsys calls free_css_id() function. This is because
> - * the lifetime of cgroup_subsys_state is subsys's matter.
> + * CSS ID must be assigned by subsys itself at cgroup creation and deleted
> + * when subsys calls free_css_id() function. This is because the life time of
> + * of cgroup_subsys_state is subsys's matter.
> + *
> + * ID->css look up is available after cgroup's directory is populated.
>   *
>   * Looking up and scanning function should be called under rcu_read_lock().
>   * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
> @@ -593,10 +595,10 @@ int cgroup_attach_task_current_cg(struct
>   * destroyed". The caller should check css and cgroup's status.
>   */
>  
> -/*
> - * Typically Called at ->destroy(), or somewhere the subsys frees
> - * cgroup_subsys_state.
> - */
> +/* Should be called in ->create() by subsys itself */
> +int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *newgr,
> +		struct cgroup_subsys_state *css);
> +/* Typically Called at ->destroy(), or somewhere the subsys frees css */
>  void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
>  
>  /* Find a cgroup_subsys_state which has given ID */
> Index: mmotm-0811/mm/memcontrol.c
> ===================================================================
> --- mmotm-0811.orig/mm/memcontrol.c
> +++ mmotm-0811/mm/memcontrol.c
> @@ -4141,6 +4141,11 @@ mem_cgroup_create(struct cgroup_subsys *
>  		if (alloc_mem_cgroup_per_zone_info(mem, node))
>  			goto free_out;
>  
> +	error = alloc_css_id(ss, cont, &mem->css);
> +	if (error)
> +		goto free_out;
> +	/* Here, css_id(&mem->css) works. but css_lookup(id)->mem doesn't */
> +
>  	/* root ? */
>  	if (cont->parent == NULL) {
>  		int cpu;
> Index: mmotm-0811/block/blk-cgroup.c
> ===================================================================
> --- mmotm-0811.orig/block/blk-cgroup.c
> +++ mmotm-0811/block/blk-cgroup.c
> @@ -958,9 +958,13 @@ blkiocg_create(struct cgroup_subsys *sub
>  {
>  	struct blkio_cgroup *blkcg;
>  	struct cgroup *parent = cgroup->parent;
> +	int ret;
>  
>  	if (!parent) {
>  		blkcg = &blkio_root_cgroup;
> +		ret = alloc_css_id(subsys, cgroup, &blkcg->css);
> +		if (ret)
> +			return ERR_PTR(ret);
>  		goto done;
>  	}
>  
> @@ -971,6 +975,11 @@ blkiocg_create(struct cgroup_subsys *sub
>  	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
>  	if (!blkcg)
>  		return ERR_PTR(-ENOMEM);
> +	ret = alloc_css_id(subsys, cgroup, &blkcg->css);
> +	if (ret) {
> +		kfree(blkcg);
> +		return ERR_PTR(ret);
> +	}
>  
>  	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
>  done:
> 

Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:06:40 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, css'id is allocated after ->create() is called. But to make use of ID
> in ->create(), it should be available before ->create().
> 
> In another thinking, considering the ID is tightly coupled with "css",
> it should be allocated when "css" is allocated.
> This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> memory and blkio are useing ID. (To support complicated hierarchy walk.)
> 
> ID will be used in mem cgroup's ->create(), later.
> 
> Note:
> If someone changes rules of css allocation, ID allocation should be moved too.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
I think we need some signs from Paul and Li, but anyway

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Thanks,
Daisuke Nishimura.

> ---
>  block/blk-cgroup.c     |    9 ++++++++
>  include/linux/cgroup.h |   16 ++++++++-------
>  kernel/cgroup.c        |   50 ++++++++++++++-----------------------------------
>  mm/memcontrol.c        |    5 ++++
>  4 files changed, 38 insertions(+), 42 deletions(-)
> 
> Index: mmotm-0811/kernel/cgroup.c
> ===================================================================
> --- mmotm-0811.orig/kernel/cgroup.c
> +++ mmotm-0811/kernel/cgroup.c
> @@ -289,9 +289,6 @@ struct cg_cgroup_link {
>  static struct css_set init_css_set;
>  static struct cg_cgroup_link init_css_set_link;
>  
> -static int cgroup_init_idr(struct cgroup_subsys *ss,
> -			   struct cgroup_subsys_state *css);
> -
>  /* css_set_lock protects the list of css_set objects, and the
>   * chain of tasks off each css_set.  Nests outside task->alloc_lock
>   * due to cgroup_iter_start() */
> @@ -770,9 +767,6 @@ static struct backing_dev_info cgroup_ba
>  	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
>  };
>  
> -static int alloc_css_id(struct cgroup_subsys *ss,
> -			struct cgroup *parent, struct cgroup *child);
> -
>  static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
>  {
>  	struct inode *inode = new_inode(sb);
> @@ -3257,7 +3251,8 @@ static void init_cgroup_css(struct cgrou
>  	css->cgroup = cgrp;
>  	atomic_set(&css->refcnt, 1);
>  	css->flags = 0;
> -	css->id = NULL;
> +	if (!ss->use_id)
> +		css->id = NULL;
>  	if (cgrp == dummytop)
>  		set_bit(CSS_ROOT, &css->flags);
>  	BUG_ON(cgrp->subsys[ss->subsys_id]);
> @@ -3342,12 +3337,6 @@ static long cgroup_create(struct cgroup 
>  			goto err_destroy;
>  		}
>  		init_cgroup_css(css, ss, cgrp);
> -		if (ss->use_id) {
> -			err = alloc_css_id(ss, parent, cgrp);
> -			if (err)
> -				goto err_destroy;
> -		}
> -		/* At error, ->destroy() callback has to free assigned ID. */
>  	}
>  
>  	cgroup_lock_hierarchy(root);
> @@ -3709,17 +3698,6 @@ int __init_or_module cgroup_load_subsys(
>  
>  	/* our new subsystem will be attached to the dummy hierarchy. */
>  	init_cgroup_css(css, ss, dummytop);
> -	/* init_idr must be after init_cgroup_css because it sets css->id. */
> -	if (ss->use_id) {
> -		int ret = cgroup_init_idr(ss, css);
> -		if (ret) {
> -			dummytop->subsys[ss->subsys_id] = NULL;
> -			ss->destroy(ss, dummytop);
> -			subsys[i] = NULL;
> -			mutex_unlock(&cgroup_mutex);
> -			return ret;
> -		}
> -	}
>  
>  	/*
>  	 * Now we need to entangle the css into the existing css_sets. unlike
> @@ -3888,8 +3866,6 @@ int __init cgroup_init(void)
>  		struct cgroup_subsys *ss = subsys[i];
>  		if (!ss->early_init)
>  			cgroup_init_subsys(ss);
> -		if (ss->use_id)
> -			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
>  	}
>  
>  	/* Add init_css_set to the hash table */
> @@ -4603,8 +4579,8 @@ err_out:
>  
>  }
>  
> -static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
> -					    struct cgroup_subsys_state *rootcss)
> +static int cgroup_init_idr(struct cgroup_subsys *ss,
> +			    struct cgroup_subsys_state *rootcss)
>  {
>  	struct css_id *newid;
>  
> @@ -4616,21 +4592,25 @@ static int __init_or_module cgroup_init_
>  		return PTR_ERR(newid);
>  
>  	newid->stack[0] = newid->id;
> -	newid->css = rootcss;
> -	rootcss->id = newid;
> +	rcu_assign_pointer(newid->css, rootcss);
> +	rcu_assign_pointer(rootcss->id, newid);
>  	return 0;
>  }
>  
> -static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
> -			struct cgroup *child)
> +int alloc_css_id(struct cgroup_subsys *ss,
> +	struct cgroup *cgrp, struct cgroup_subsys_state *css)
>  {
>  	int subsys_id, i, depth = 0;
> -	struct cgroup_subsys_state *parent_css, *child_css;
> +	struct cgroup_subsys_state *parent_css;
> +	struct cgroup *parent;
>  	struct css_id *child_id, *parent_id;
>  
> +	if (cgrp == dummytop)
> +		return cgroup_init_idr(ss, css);
> +
> +	parent = cgrp->parent;
>  	subsys_id = ss->subsys_id;
>  	parent_css = parent->subsys[subsys_id];
> -	child_css = child->subsys[subsys_id];
>  	parent_id = parent_css->id;
>  	depth = parent_id->depth + 1;
>  
> @@ -4645,7 +4625,7 @@ static int alloc_css_id(struct cgroup_su
>  	 * child_id->css pointer will be set after this cgroup is available
>  	 * see cgroup_populate_dir()
>  	 */
> -	rcu_assign_pointer(child_css->id, child_id);
> +	rcu_assign_pointer(css->id, child_id);
>  
>  	return 0;
>  }
> Index: mmotm-0811/include/linux/cgroup.h
> ===================================================================
> --- mmotm-0811.orig/include/linux/cgroup.h
> +++ mmotm-0811/include/linux/cgroup.h
> @@ -583,9 +583,11 @@ int cgroup_attach_task_current_cg(struct
>  /*
>   * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
>   * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
> - * CSS ID is assigned at cgroup allocation (create) automatically
> - * and removed when subsys calls free_css_id() function. This is because
> - * the lifetime of cgroup_subsys_state is subsys's matter.
> + * CSS ID must be assigned by subsys itself at cgroup creation and deleted
> + * when subsys calls free_css_id() function. This is because the life time of
> + * of cgroup_subsys_state is subsys's matter.
> + *
> + * ID->css look up is available after cgroup's directory is populated.
>   *
>   * Looking up and scanning function should be called under rcu_read_lock().
>   * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
> @@ -593,10 +595,10 @@ int cgroup_attach_task_current_cg(struct
>   * destroyed". The caller should check css and cgroup's status.
>   */
>  
> -/*
> - * Typically Called at ->destroy(), or somewhere the subsys frees
> - * cgroup_subsys_state.
> - */
> +/* Should be called in ->create() by subsys itself */
> +int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *newgr,
> +		struct cgroup_subsys_state *css);
> +/* Typically Called at ->destroy(), or somewhere the subsys frees css */
>  void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
>  
>  /* Find a cgroup_subsys_state which has given ID */
> Index: mmotm-0811/mm/memcontrol.c
> ===================================================================
> --- mmotm-0811.orig/mm/memcontrol.c
> +++ mmotm-0811/mm/memcontrol.c
> @@ -4141,6 +4141,11 @@ mem_cgroup_create(struct cgroup_subsys *
>  		if (alloc_mem_cgroup_per_zone_info(mem, node))
>  			goto free_out;
>  
> +	error = alloc_css_id(ss, cont, &mem->css);
> +	if (error)
> +		goto free_out;
> +	/* Here, css_id(&mem->css) works. but css_lookup(id)->mem doesn't */
> +
>  	/* root ? */
>  	if (cont->parent == NULL) {
>  		int cpu;
> Index: mmotm-0811/block/blk-cgroup.c
> ===================================================================
> --- mmotm-0811.orig/block/blk-cgroup.c
> +++ mmotm-0811/block/blk-cgroup.c
> @@ -958,9 +958,13 @@ blkiocg_create(struct cgroup_subsys *sub
>  {
>  	struct blkio_cgroup *blkcg;
>  	struct cgroup *parent = cgroup->parent;
> +	int ret;
>  
>  	if (!parent) {
>  		blkcg = &blkio_root_cgroup;
> +		ret = alloc_css_id(subsys, cgroup, &blkcg->css);
> +		if (ret)
> +			return ERR_PTR(ret);
>  		goto done;
>  	}
>  
> @@ -971,6 +975,11 @@ blkiocg_create(struct cgroup_subsys *sub
>  	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
>  	if (!blkcg)
>  		return ERR_PTR(-ENOMEM);
> +	ret = alloc_css_id(subsys, cgroup, &blkcg->css);
> +	if (ret) {
> +		kfree(blkcg);
> +		return ERR_PTR(ret);
> +	}
>  
>  	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
>  done:
> 

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Re: [PATCH 2/5] memcg: quick memcg lookup array

[Daisuke Nishimura]

> Index: mmotm-0811/mm/memcontrol.c
> ===================================================================
> --- mmotm-0811.orig/mm/memcontrol.c
> +++ mmotm-0811/mm/memcontrol.c
> @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
>   */
>  struct mem_cgroup {
>  	struct cgroup_subsys_state css;
> +	int	valid; /* for checking validness under RCU access.*/
>  	/*
>  	 * the counter to account for memory usage
>  	 */
Do we really need to add this new member ?
Can't we safely access "mem(=rcu_dereference(mem_cgroup[id]))" under rcu_read_lock() ?
(iow, "mem" is not freed ?)


> @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
>  	mem_cgroup_remove_from_trees(mem);
>  	free_css_id(&mem_cgroup_subsys, &mem->css);
>  
> +	atomic_dec(&mem_cgroup_num);
>  	for_each_node_state(node, N_POSSIBLE)
>  		free_mem_cgroup_per_zone_info(mem, node);
>  
> @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
>  		vfree(mem);
>  }
>  
> +static void mem_cgroup_free(struct mem_cgroup *mem)
> +{
> +	/* No more lookup */
> +	mem->valid = 0;
> +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> +	/*
> +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> + 	 * call_rcu();
> + 	 */
> +	synchronize_rcu();
> +	__mem_cgroup_free(mem);
> +}
> +
>  static void mem_cgroup_get(struct mem_cgroup *mem)
>  {
>  	atomic_inc(&mem->refcnt);
> @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
>  {
>  	if (atomic_sub_and_test(count, &mem->refcnt)) {
>  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> -		__mem_cgroup_free(mem);
> +		mem_cgroup_free(mem);
>  		if (parent)
>  			mem_cgroup_put(parent);
>  	}
> @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
>  	atomic_set(&mem->refcnt, 1);
>  	mem->move_charge_at_immigrate = 0;
>  	mutex_init(&mem->thresholds_lock);
> +	atomic_inc(&mem_cgroup_num);
> +	register_memcg_id(mem);
>  	return &mem->css;
>  free_out:
> -	__mem_cgroup_free(mem);
> +	mem_cgroup_free(mem);
>  	root_mem_cgroup = NULL;
>  	return ERR_PTR(error);
>  }
I think mem_cgroup_num should be increased at mem_cgroup_alloc(), because it
is decreased at __mem_cgroup_free(). Otherwise, it can be decreased while it
has not been increased, if mem_cgroup_create() fails after mem_cgroup_alloc().


Thanks,
Daisuke Nishimura.

Re: [PATCH 2/5] memcg: quick memcg lookup array

[Daisuke Nishimura]

> Index: mmotm-0811/mm/memcontrol.c
> ===================================================================
> --- mmotm-0811.orig/mm/memcontrol.c
> +++ mmotm-0811/mm/memcontrol.c
> @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
>   */
>  struct mem_cgroup {
>  	struct cgroup_subsys_state css;
> +	int	valid; /* for checking validness under RCU access.*/
>  	/*
>  	 * the counter to account for memory usage
>  	 */
Do we really need to add this new member ?
Can't we safely access "mem(=rcu_dereference(mem_cgroup[id]))" under rcu_read_lock() ?
(iow, "mem" is not freed ?)


> @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
>  	mem_cgroup_remove_from_trees(mem);
>  	free_css_id(&mem_cgroup_subsys, &mem->css);
>  
> +	atomic_dec(&mem_cgroup_num);
>  	for_each_node_state(node, N_POSSIBLE)
>  		free_mem_cgroup_per_zone_info(mem, node);
>  
> @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
>  		vfree(mem);
>  }
>  
> +static void mem_cgroup_free(struct mem_cgroup *mem)
> +{
> +	/* No more lookup */
> +	mem->valid = 0;
> +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> +	/*
> +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> + 	 * call_rcu();
> + 	 */
> +	synchronize_rcu();
> +	__mem_cgroup_free(mem);
> +}
> +
>  static void mem_cgroup_get(struct mem_cgroup *mem)
>  {
>  	atomic_inc(&mem->refcnt);
> @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
>  {
>  	if (atomic_sub_and_test(count, &mem->refcnt)) {
>  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> -		__mem_cgroup_free(mem);
> +		mem_cgroup_free(mem);
>  		if (parent)
>  			mem_cgroup_put(parent);
>  	}
> @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
>  	atomic_set(&mem->refcnt, 1);
>  	mem->move_charge_at_immigrate = 0;
>  	mutex_init(&mem->thresholds_lock);
> +	atomic_inc(&mem_cgroup_num);
> +	register_memcg_id(mem);
>  	return &mem->css;
>  free_out:
> -	__mem_cgroup_free(mem);
> +	mem_cgroup_free(mem);
>  	root_mem_cgroup = NULL;
>  	return ERR_PTR(error);
>  }
I think mem_cgroup_num should be increased at mem_cgroup_alloc(), because it
is decreased at __mem_cgroup_free(). Otherwise, it can be decreased while it
has not been increased, if mem_cgroup_create() fails after mem_cgroup_alloc().


Thanks,
Daisuke Nishimura.

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Re: [PATCH 3/5] memcg: use ID instead of pointer in page_cgroup

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:09:00 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, addresses of memory cgroup can be calculated by their ID without complex.
> This patch relplaces pc->mem_cgroup from a pointer to a unsigned short.
> On 64bit architecture, this offers us more 6bytes room per page_cgroup.
> Use 2bytes for blkio-cgroup's page tracking. More 4bytes will be used for
> some light-weight concurrent access.
> 
> We may able to move this id onto flags field but ...go step by step.
> 
> Changelog: 20100824
>  - fixed comments, and typo.
> Changelog: 20100811
>  - using new rcu APIs, as rcu_dereference_check() etc.
> Changelog: 20100804
>  - added comments to page_cgroup.h
> Changelog: 20100730
>  - fixed some garbage added by debug code in early stage
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Re: [PATCH 3/5] memcg: use ID instead of pointer in page_cgroup

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:09:00 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, addresses of memory cgroup can be calculated by their ID without complex.
> This patch relplaces pc->mem_cgroup from a pointer to a unsigned short.
> On 64bit architecture, this offers us more 6bytes room per page_cgroup.
> Use 2bytes for blkio-cgroup's page tracking. More 4bytes will be used for
> some light-weight concurrent access.
> 
> We may able to move this id onto flags field but ...go step by step.
> 
> Changelog: 20100824
>  - fixed comments, and typo.
> Changelog: 20100811
>  - using new rcu APIs, as rcu_dereference_check() etc.
> Changelog: 20100804
>  - added comments to page_cgroup.h
> Changelog: 20100730
>  - fixed some garbage added by debug code in early stage
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

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Re: [PATCH 4/5] memcg: lockless update of file stat with move-account safe method

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:10:50 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> At accounting file events per memory cgroup, we need to find memory cgroup
> via page_cgroup->mem_cgroup. Now, we use lock_page_cgroup().
> 
> But, considering the context which page-cgroup for files are accessed,
> we can use alternative light-weight mutual execusion in the most case.
> At handling file-caches, the only race we have to take care of is "moving"
> account, IOW, overwriting page_cgroup->mem_cgroup. Because file status
> update is done while the page-cache is in stable state, we don't have to
> take care of race with charge/uncharge.
> 
> Unlike charge/uncharge, "move" happens not so frequently. It happens only when
> rmdir() and task-moving (with a special settings.)
> This patch adds a race-checker for file-cache-status accounting v.s. account
> moving. The new per-cpu-per-memcg counter MEM_CGROUP_ON_MOVE is added.
> The routine for account move 
>   1. Increment it before start moving
>   2. Call synchronize_rcu()
>   3. Decrement it after the end of moving.
> By this, file-status-counting routine can check it needs to call
> lock_page_cgroup(). In most case, I doesn't need to call it.
> 
> Changelog: 20100825
>  - added a comment about mc.lock
>  - fixed bad lock.
> Changelog: 20100804
>  - added a comment for possible optimization hint.
> Changelog: 20100730
>  - some cleanup.
> Changelog: 20100729
>  - replaced __this_cpu_xxx() with this_cpu_xxx
>    (because we don't call spinlock)
>  - added VM_BUG_ON().
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

(snip)

> @@ -1505,29 +1551,36 @@ void mem_cgroup_update_file_mapped(struc
>  {
>  	struct mem_cgroup *mem;
>  	struct page_cgroup *pc;
> +	bool need_lock = false;
>  
>  	pc = lookup_page_cgroup(page);
>  	if (unlikely(!pc))
>  		return;
> -
> -	lock_page_cgroup(pc);
> +	rcu_read_lock();
>  	mem = id_to_memcg(pc->mem_cgroup, true);
It doesn't cause any problem, but I think it would be better to change this to
"id_to_memcg(..., false)". It's just under rcu_read_lock(), not under page_cgroup
lock anymore.

Otherwise, it looks good to me.

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Thanks,
Daisuke Nishimura.

Re: [PATCH 4/5] memcg: lockless update of file stat with move-account safe method

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:10:50 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> At accounting file events per memory cgroup, we need to find memory cgroup
> via page_cgroup->mem_cgroup. Now, we use lock_page_cgroup().
> 
> But, considering the context which page-cgroup for files are accessed,
> we can use alternative light-weight mutual execusion in the most case.
> At handling file-caches, the only race we have to take care of is "moving"
> account, IOW, overwriting page_cgroup->mem_cgroup. Because file status
> update is done while the page-cache is in stable state, we don't have to
> take care of race with charge/uncharge.
> 
> Unlike charge/uncharge, "move" happens not so frequently. It happens only when
> rmdir() and task-moving (with a special settings.)
> This patch adds a race-checker for file-cache-status accounting v.s. account
> moving. The new per-cpu-per-memcg counter MEM_CGROUP_ON_MOVE is added.
> The routine for account move 
>   1. Increment it before start moving
>   2. Call synchronize_rcu()
>   3. Decrement it after the end of moving.
> By this, file-status-counting routine can check it needs to call
> lock_page_cgroup(). In most case, I doesn't need to call it.
> 
> Changelog: 20100825
>  - added a comment about mc.lock
>  - fixed bad lock.
> Changelog: 20100804
>  - added a comment for possible optimization hint.
> Changelog: 20100730
>  - some cleanup.
> Changelog: 20100729
>  - replaced __this_cpu_xxx() with this_cpu_xxx
>    (because we don't call spinlock)
>  - added VM_BUG_ON().
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

(snip)

> @@ -1505,29 +1551,36 @@ void mem_cgroup_update_file_mapped(struc
>  {
>  	struct mem_cgroup *mem;
>  	struct page_cgroup *pc;
> +	bool need_lock = false;
>  
>  	pc = lookup_page_cgroup(page);
>  	if (unlikely(!pc))
>  		return;
> -
> -	lock_page_cgroup(pc);
> +	rcu_read_lock();
>  	mem = id_to_memcg(pc->mem_cgroup, true);
It doesn't cause any problem, but I think it would be better to change this to
"id_to_memcg(..., false)". It's just under rcu_read_lock(), not under page_cgroup
lock anymore.

Otherwise, it looks good to me.

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Thanks,
Daisuke Nishimura.

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Re: [PATCH 5/5] memcg: generic file stat accounting interface

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:11:40 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Preparing for adding new status arounf file caches.(dirty, writeback,etc..)
> Using a unified macro and more generic names.
> All counters will have the same rule for updating.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

one nitpick.

> @@ -2042,17 +2031,20 @@ static void __mem_cgroup_commit_charge(s
>  static void __mem_cgroup_move_account(struct page_cgroup *pc,
>  	struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
>  {
> +	int i;
>  	VM_BUG_ON(from == to);
>  	VM_BUG_ON(PageLRU(pc->page));
>  	VM_BUG_ON(!PageCgroupLocked(pc));
>  	VM_BUG_ON(!PageCgroupUsed(pc));
>  	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
>  
> -	if (PageCgroupFileMapped(pc)) {
> +	for (i = MEM_CGROUP_FSTAT_BASE; i < MEM_CGROUP_FSTAT_END; ++i) {
> +		if (!test_bit(fflag_idx(MEMCG_FSTAT_IDX(i)), &pc->flags))
> +			continue;
>  		/* Update mapped_file data for mem_cgroup */
It might be better to update this comment too.

	/* Update file-stat data for mem_cgroup */

or something ?

Thanks,
Daisuke Nishimura.

Re: [PATCH 5/5] memcg: generic file stat accounting interface

[Daisuke Nishimura]

On Wed, 25 Aug 2010 17:11:40 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Preparing for adding new status arounf file caches.(dirty, writeback,etc..)
> Using a unified macro and more generic names.
> All counters will have the same rule for updating.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

one nitpick.

> @@ -2042,17 +2031,20 @@ static void __mem_cgroup_commit_charge(s
>  static void __mem_cgroup_move_account(struct page_cgroup *pc,
>  	struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
>  {
> +	int i;
>  	VM_BUG_ON(from == to);
>  	VM_BUG_ON(PageLRU(pc->page));
>  	VM_BUG_ON(!PageCgroupLocked(pc));
>  	VM_BUG_ON(!PageCgroupUsed(pc));
>  	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
>  
> -	if (PageCgroupFileMapped(pc)) {
> +	for (i = MEM_CGROUP_FSTAT_BASE; i < MEM_CGROUP_FSTAT_END; ++i) {
> +		if (!test_bit(fflag_idx(MEMCG_FSTAT_IDX(i)), &pc->flags))
> +			continue;
>  		/* Update mapped_file data for mem_cgroup */
It might be better to update this comment too.

	/* Update file-stat data for mem_cgroup */

or something ?

Thanks,
Daisuke Nishimura.

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Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-26 09:13:46]:

> On Wed, 25 Aug 2010 19:45:00 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:06:40]:
> > 
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > 
> > > Now, css'id is allocated after ->create() is called. But to make use of ID
> > > in ->create(), it should be available before ->create().
> > > 
> > > In another thinking, considering the ID is tightly coupled with "css",
> > > it should be allocated when "css" is allocated.
> > > This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> > > memory and blkio are useing ID. (To support complicated hierarchy walk.)
> >                        ^^^^ typo
> > > 
> > > ID will be used in mem cgroup's ->create(), later.
> > > 
> > > Note:
> > > If someone changes rules of css allocation, ID allocation should be moved too.
> > > 
> > 
> > What rules? could you please elaborate?
> > 
> See Paul Menage's mail. He said "allocating css object under kernel/cgroup.c
> will make kernel/cgroup.c cleaner." But it seems too big for my purpose.
> 
> > Seems cleaner, may be we need to update cgroups.txt?
> 
> Hmm. will look into.
>

OK, the patch looks good to me otherwise

 
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 

-- 
	Three Cheers,
	Balbir

Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-26 09:13:46]:

> On Wed, 25 Aug 2010 19:45:00 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:06:40]:
> > 
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > 
> > > Now, css'id is allocated after ->create() is called. But to make use of ID
> > > in ->create(), it should be available before ->create().
> > > 
> > > In another thinking, considering the ID is tightly coupled with "css",
> > > it should be allocated when "css" is allocated.
> > > This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> > > memory and blkio are useing ID. (To support complicated hierarchy walk.)
> >                        ^^^^ typo
> > > 
> > > ID will be used in mem cgroup's ->create(), later.
> > > 
> > > Note:
> > > If someone changes rules of css allocation, ID allocation should be moved too.
> > > 
> > 
> > What rules? could you please elaborate?
> > 
> See Paul Menage's mail. He said "allocating css object under kernel/cgroup.c
> will make kernel/cgroup.c cleaner." But it seems too big for my purpose.
> 
> > Seems cleaner, may be we need to update cgroups.txt?
> 
> Hmm. will look into.
>

OK, the patch looks good to me otherwise

 
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 

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	Three Cheers,
	Balbir

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Re: [PATCH 2/5] memcg: quick memcg lookup array

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:07:41]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, memory cgroup has an ID per cgroup and make use of it at
>  - hierarchy walk,
>  - swap recording.
> 
> This patch is for making more use of it. The final purpose is
> to replace page_cgroup->mem_cgroup's pointer to an unsigned short.
> 
> This patch caches a pointer of memcg in an array. By this, we
> don't have to call css_lookup() which requires radix-hash walk.
> This saves some amount of memory footprint at lookup memcg via id.
> 
> Changelog: 20100825
>  - applied comments.
> 
> Changelog: 20100811
>  - adjusted onto mmotm-2010-08-11
>  - fixed RCU related parts.
>  - use attach_id() callback.
> 
> Changelog: 20100804
>  - fixed description in init/Kconfig
> 
> Changelog: 20100730
>  - fixed rcu_read_unlock() placement.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  init/Kconfig    |   10 +++++++
>  mm/memcontrol.c |   75 +++++++++++++++++++++++++++++++++++++++++---------------
>  2 files changed, 65 insertions(+), 20 deletions(-)
> 
> Index: mmotm-0811/mm/memcontrol.c
> ===================================================================
> --- mmotm-0811.orig/mm/memcontrol.c
> +++ mmotm-0811/mm/memcontrol.c
> @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
>   */
>  struct mem_cgroup {
>  	struct cgroup_subsys_state css;
> +	int	valid; /* for checking validness under RCU access.*/
>  	/*
>  	 * the counter to account for memory usage
>  	 */
> @@ -294,6 +295,29 @@ static bool move_file(void)
>  					&mc.to->move_charge_at_immigrate);
>  }
> 
> +/* 0 is unused */
> +static atomic_t mem_cgroup_num;
> +#define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
> +static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
> +
> +/* Must be called under rcu_read_lock */
> +static struct mem_cgroup *id_to_memcg(unsigned short id)
> +{
> +	struct mem_cgroup *mem;
> +	/* see mem_cgroup_free() */
> +	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
> +	if (likely(mem && mem->valid))
> +		return mem;
> +	return NULL;
> +}
> +
> +static void register_memcg_id(struct mem_cgroup *mem)
> +{
> +	int id = css_id(&mem->css);
> +	rcu_assign_pointer(mem_cgroups[id], mem);
> +	VM_BUG_ON(!mem->valid);
> +}
> +
>  /*
>   * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
>   * limit reclaim to prevent infinite loops, if they ever occur.
> @@ -1847,18 +1871,7 @@ static void mem_cgroup_cancel_charge(str
>   * it's concern. (dropping refcnt from swap can be called against removed
>   * memcg.)
>   */
> -static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
> -{
> -	struct cgroup_subsys_state *css;
> 
> -	/* ID 0 is unused ID */
> -	if (!id)
> -		return NULL;
> -	css = css_lookup(&mem_cgroup_subsys, id);
> -	if (!css)
> -		return NULL;
> -	return container_of(css, struct mem_cgroup, css);
> -}
> 
>  struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
>  {
> @@ -1879,7 +1892,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr
>  		ent.val = page_private(page);
>  		id = lookup_swap_cgroup(ent);
>  		rcu_read_lock();
> -		mem = mem_cgroup_lookup(id);
> +		mem = id_to_memcg(id);
>  		if (mem && !css_tryget(&mem->css))
>  			mem = NULL;
>  		rcu_read_unlock();
> @@ -2231,7 +2244,7 @@ __mem_cgroup_commit_charge_swapin(struct
> 
>  		id = swap_cgroup_record(ent, 0);
>  		rcu_read_lock();
> -		memcg = mem_cgroup_lookup(id);
> +		memcg = id_to_memcg(id);
>  		if (memcg) {
>  			/*
>  			 * This recorded memcg can be obsolete one. So, avoid
> @@ -2240,9 +2253,10 @@ __mem_cgroup_commit_charge_swapin(struct
>  			if (!mem_cgroup_is_root(memcg))
>  				res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
>  			mem_cgroup_swap_statistics(memcg, false);
> +			rcu_read_unlock();
>  			mem_cgroup_put(memcg);
> -		}
> -		rcu_read_unlock();
> +		} else
> +			rcu_read_unlock();
>  	}
>  	/*
>  	 * At swapin, we may charge account against cgroup which has no tasks.
> @@ -2495,7 +2509,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
> 
>  	id = swap_cgroup_record(ent, 0);
>  	rcu_read_lock();
> -	memcg = mem_cgroup_lookup(id);
> +	memcg = id_to_memcg(id);
>  	if (memcg) {
>  		/*
>  		 * We uncharge this because swap is freed.
> @@ -2504,9 +2518,10 @@ void mem_cgroup_uncharge_swap(swp_entry_
>  		if (!mem_cgroup_is_root(memcg))
>  			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
>  		mem_cgroup_swap_statistics(memcg, false);
> +		rcu_read_unlock();
>  		mem_cgroup_put(memcg);
> -	}
> -	rcu_read_unlock();
> +	} else
> +		rcu_read_unlock();
>  }
> 
>  /**
> @@ -4010,6 +4025,9 @@ static struct mem_cgroup *mem_cgroup_all
>  	struct mem_cgroup *mem;
>  	int size = sizeof(struct mem_cgroup);
> 
> +	if (atomic_read(&mem_cgroup_num) == NR_MEMCG_GROUPS)
> +		return NULL;
> +
>  	/* Can be very big if MAX_NUMNODES is very big */
>  	if (size < PAGE_SIZE)
>  		mem = kmalloc(size, GFP_KERNEL);
> @@ -4020,6 +4038,7 @@ static struct mem_cgroup *mem_cgroup_all
>  		return NULL;
> 
>  	memset(mem, 0, size);
> +	mem->valid = 1;
>  	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
>  	if (!mem->stat) {
>  		if (size < PAGE_SIZE)
> @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
>  	mem_cgroup_remove_from_trees(mem);
>  	free_css_id(&mem_cgroup_subsys, &mem->css);
> 
> +	atomic_dec(&mem_cgroup_num);
>  	for_each_node_state(node, N_POSSIBLE)
>  		free_mem_cgroup_per_zone_info(mem, node);
> 
> @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
>  		vfree(mem);
>  }
> 
> +static void mem_cgroup_free(struct mem_cgroup *mem)
> +{
> +	/* No more lookup */
> +	mem->valid = 0;
> +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> +	/*
> +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> + 	 * call_rcu();
> + 	 */
> +	synchronize_rcu();
> +	__mem_cgroup_free(mem);
> +}
> +
>  static void mem_cgroup_get(struct mem_cgroup *mem)
>  {
>  	atomic_inc(&mem->refcnt);
> @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
>  {
>  	if (atomic_sub_and_test(count, &mem->refcnt)) {
>  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> -		__mem_cgroup_free(mem);
> +		mem_cgroup_free(mem);
>  		if (parent)
>  			mem_cgroup_put(parent);
>  	}
> @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
>  	atomic_set(&mem->refcnt, 1);
>  	mem->move_charge_at_immigrate = 0;
>  	mutex_init(&mem->thresholds_lock);
> +	atomic_inc(&mem_cgroup_num);
> +	register_memcg_id(mem);
>  	return &mem->css;
>  free_out:
> -	__mem_cgroup_free(mem);
> +	mem_cgroup_free(mem);
>  	root_mem_cgroup = NULL;
>  	return ERR_PTR(error);
>  }
> Index: mmotm-0811/init/Kconfig
> ===================================================================
> --- mmotm-0811.orig/init/Kconfig
> +++ mmotm-0811/init/Kconfig
> @@ -594,6 +594,16 @@ config CGROUP_MEM_RES_CTLR_SWAP
>  	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
>  	  size is 4096bytes, 512k per 1Gbytes of swap.
> 
> +config MEM_CGROUP_MAX_GROUPS
> +	int "Maximum number of memory cgroups on a system"
> +	range 1 65535
> +	default 8192 if 64BIT
> +	default 2048 if 32BIT
> +	help
> +	  Memory cgroup has limitation of the number of groups created.
> +	  Please select your favorite value. The more you allow, the more
> +	  memory(a pointer per group) will be consumed.
> +

Looks good, quick thought - should we expost memcg->id to user space
through a config file? I don't see any reason at this point, unless we
do it for all controllers.

-- 
	Three Cheers,
	Balbir

Re: [PATCH 2/5] memcg: quick memcg lookup array

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:07:41]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Now, memory cgroup has an ID per cgroup and make use of it at
>  - hierarchy walk,
>  - swap recording.
> 
> This patch is for making more use of it. The final purpose is
> to replace page_cgroup->mem_cgroup's pointer to an unsigned short.
> 
> This patch caches a pointer of memcg in an array. By this, we
> don't have to call css_lookup() which requires radix-hash walk.
> This saves some amount of memory footprint at lookup memcg via id.
> 
> Changelog: 20100825
>  - applied comments.
> 
> Changelog: 20100811
>  - adjusted onto mmotm-2010-08-11
>  - fixed RCU related parts.
>  - use attach_id() callback.
> 
> Changelog: 20100804
>  - fixed description in init/Kconfig
> 
> Changelog: 20100730
>  - fixed rcu_read_unlock() placement.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  init/Kconfig    |   10 +++++++
>  mm/memcontrol.c |   75 +++++++++++++++++++++++++++++++++++++++++---------------
>  2 files changed, 65 insertions(+), 20 deletions(-)
> 
> Index: mmotm-0811/mm/memcontrol.c
> ===================================================================
> --- mmotm-0811.orig/mm/memcontrol.c
> +++ mmotm-0811/mm/memcontrol.c
> @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
>   */
>  struct mem_cgroup {
>  	struct cgroup_subsys_state css;
> +	int	valid; /* for checking validness under RCU access.*/
>  	/*
>  	 * the counter to account for memory usage
>  	 */
> @@ -294,6 +295,29 @@ static bool move_file(void)
>  					&mc.to->move_charge_at_immigrate);
>  }
> 
> +/* 0 is unused */
> +static atomic_t mem_cgroup_num;
> +#define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
> +static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
> +
> +/* Must be called under rcu_read_lock */
> +static struct mem_cgroup *id_to_memcg(unsigned short id)
> +{
> +	struct mem_cgroup *mem;
> +	/* see mem_cgroup_free() */
> +	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
> +	if (likely(mem && mem->valid))
> +		return mem;
> +	return NULL;
> +}
> +
> +static void register_memcg_id(struct mem_cgroup *mem)
> +{
> +	int id = css_id(&mem->css);
> +	rcu_assign_pointer(mem_cgroups[id], mem);
> +	VM_BUG_ON(!mem->valid);
> +}
> +
>  /*
>   * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
>   * limit reclaim to prevent infinite loops, if they ever occur.
> @@ -1847,18 +1871,7 @@ static void mem_cgroup_cancel_charge(str
>   * it's concern. (dropping refcnt from swap can be called against removed
>   * memcg.)
>   */
> -static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
> -{
> -	struct cgroup_subsys_state *css;
> 
> -	/* ID 0 is unused ID */
> -	if (!id)
> -		return NULL;
> -	css = css_lookup(&mem_cgroup_subsys, id);
> -	if (!css)
> -		return NULL;
> -	return container_of(css, struct mem_cgroup, css);
> -}
> 
>  struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
>  {
> @@ -1879,7 +1892,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr
>  		ent.val = page_private(page);
>  		id = lookup_swap_cgroup(ent);
>  		rcu_read_lock();
> -		mem = mem_cgroup_lookup(id);
> +		mem = id_to_memcg(id);
>  		if (mem && !css_tryget(&mem->css))
>  			mem = NULL;
>  		rcu_read_unlock();
> @@ -2231,7 +2244,7 @@ __mem_cgroup_commit_charge_swapin(struct
> 
>  		id = swap_cgroup_record(ent, 0);
>  		rcu_read_lock();
> -		memcg = mem_cgroup_lookup(id);
> +		memcg = id_to_memcg(id);
>  		if (memcg) {
>  			/*
>  			 * This recorded memcg can be obsolete one. So, avoid
> @@ -2240,9 +2253,10 @@ __mem_cgroup_commit_charge_swapin(struct
>  			if (!mem_cgroup_is_root(memcg))
>  				res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
>  			mem_cgroup_swap_statistics(memcg, false);
> +			rcu_read_unlock();
>  			mem_cgroup_put(memcg);
> -		}
> -		rcu_read_unlock();
> +		} else
> +			rcu_read_unlock();
>  	}
>  	/*
>  	 * At swapin, we may charge account against cgroup which has no tasks.
> @@ -2495,7 +2509,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
> 
>  	id = swap_cgroup_record(ent, 0);
>  	rcu_read_lock();
> -	memcg = mem_cgroup_lookup(id);
> +	memcg = id_to_memcg(id);
>  	if (memcg) {
>  		/*
>  		 * We uncharge this because swap is freed.
> @@ -2504,9 +2518,10 @@ void mem_cgroup_uncharge_swap(swp_entry_
>  		if (!mem_cgroup_is_root(memcg))
>  			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
>  		mem_cgroup_swap_statistics(memcg, false);
> +		rcu_read_unlock();
>  		mem_cgroup_put(memcg);
> -	}
> -	rcu_read_unlock();
> +	} else
> +		rcu_read_unlock();
>  }
> 
>  /**
> @@ -4010,6 +4025,9 @@ static struct mem_cgroup *mem_cgroup_all
>  	struct mem_cgroup *mem;
>  	int size = sizeof(struct mem_cgroup);
> 
> +	if (atomic_read(&mem_cgroup_num) == NR_MEMCG_GROUPS)
> +		return NULL;
> +
>  	/* Can be very big if MAX_NUMNODES is very big */
>  	if (size < PAGE_SIZE)
>  		mem = kmalloc(size, GFP_KERNEL);
> @@ -4020,6 +4038,7 @@ static struct mem_cgroup *mem_cgroup_all
>  		return NULL;
> 
>  	memset(mem, 0, size);
> +	mem->valid = 1;
>  	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
>  	if (!mem->stat) {
>  		if (size < PAGE_SIZE)
> @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
>  	mem_cgroup_remove_from_trees(mem);
>  	free_css_id(&mem_cgroup_subsys, &mem->css);
> 
> +	atomic_dec(&mem_cgroup_num);
>  	for_each_node_state(node, N_POSSIBLE)
>  		free_mem_cgroup_per_zone_info(mem, node);
> 
> @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
>  		vfree(mem);
>  }
> 
> +static void mem_cgroup_free(struct mem_cgroup *mem)
> +{
> +	/* No more lookup */
> +	mem->valid = 0;
> +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> +	/*
> +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> + 	 * call_rcu();
> + 	 */
> +	synchronize_rcu();
> +	__mem_cgroup_free(mem);
> +}
> +
>  static void mem_cgroup_get(struct mem_cgroup *mem)
>  {
>  	atomic_inc(&mem->refcnt);
> @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
>  {
>  	if (atomic_sub_and_test(count, &mem->refcnt)) {
>  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> -		__mem_cgroup_free(mem);
> +		mem_cgroup_free(mem);
>  		if (parent)
>  			mem_cgroup_put(parent);
>  	}
> @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
>  	atomic_set(&mem->refcnt, 1);
>  	mem->move_charge_at_immigrate = 0;
>  	mutex_init(&mem->thresholds_lock);
> +	atomic_inc(&mem_cgroup_num);
> +	register_memcg_id(mem);
>  	return &mem->css;
>  free_out:
> -	__mem_cgroup_free(mem);
> +	mem_cgroup_free(mem);
>  	root_mem_cgroup = NULL;
>  	return ERR_PTR(error);
>  }
> Index: mmotm-0811/init/Kconfig
> ===================================================================
> --- mmotm-0811.orig/init/Kconfig
> +++ mmotm-0811/init/Kconfig
> @@ -594,6 +594,16 @@ config CGROUP_MEM_RES_CTLR_SWAP
>  	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
>  	  size is 4096bytes, 512k per 1Gbytes of swap.
> 
> +config MEM_CGROUP_MAX_GROUPS
> +	int "Maximum number of memory cgroups on a system"
> +	range 1 65535
> +	default 8192 if 64BIT
> +	default 2048 if 32BIT
> +	help
> +	  Memory cgroup has limitation of the number of groups created.
> +	  Please select your favorite value. The more you allow, the more
> +	  memory(a pointer per group) will be consumed.
> +

Looks good, quick thought - should we expost memcg->id to user space
through a config file? I don't see any reason at this point, unless we
do it for all controllers.

-- 
	Three Cheers,
	Balbir

--
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Re: [PATCH 2/5] memcg: quick memcg lookup array

[KAMEZAWA Hiroyuki]

On Tue, 31 Aug 2010 12:44:14 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:07:41]:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > Now, memory cgroup has an ID per cgroup and make use of it at
> >  - hierarchy walk,
> >  - swap recording.
> > 
> > This patch is for making more use of it. The final purpose is
> > to replace page_cgroup->mem_cgroup's pointer to an unsigned short.
> > 
> > This patch caches a pointer of memcg in an array. By this, we
> > don't have to call css_lookup() which requires radix-hash walk.
> > This saves some amount of memory footprint at lookup memcg via id.
> > 
> > Changelog: 20100825
> >  - applied comments.
> > 
> > Changelog: 20100811
> >  - adjusted onto mmotm-2010-08-11
> >  - fixed RCU related parts.
> >  - use attach_id() callback.
> > 
> > Changelog: 20100804
> >  - fixed description in init/Kconfig
> > 
> > Changelog: 20100730
> >  - fixed rcu_read_unlock() placement.
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  init/Kconfig    |   10 +++++++
> >  mm/memcontrol.c |   75 +++++++++++++++++++++++++++++++++++++++++---------------
> >  2 files changed, 65 insertions(+), 20 deletions(-)
> > 
> > Index: mmotm-0811/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0811.orig/mm/memcontrol.c
> > +++ mmotm-0811/mm/memcontrol.c
> > @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
> >   */
> >  struct mem_cgroup {
> >  	struct cgroup_subsys_state css;
> > +	int	valid; /* for checking validness under RCU access.*/
> >  	/*
> >  	 * the counter to account for memory usage
> >  	 */
> > @@ -294,6 +295,29 @@ static bool move_file(void)
> >  					&mc.to->move_charge_at_immigrate);
> >  }
> > 
> > +/* 0 is unused */
> > +static atomic_t mem_cgroup_num;
> > +#define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
> > +static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
> > +
> > +/* Must be called under rcu_read_lock */
> > +static struct mem_cgroup *id_to_memcg(unsigned short id)
> > +{
> > +	struct mem_cgroup *mem;
> > +	/* see mem_cgroup_free() */
> > +	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
> > +	if (likely(mem && mem->valid))
> > +		return mem;
> > +	return NULL;
> > +}
> > +
> > +static void register_memcg_id(struct mem_cgroup *mem)
> > +{
> > +	int id = css_id(&mem->css);
> > +	rcu_assign_pointer(mem_cgroups[id], mem);
> > +	VM_BUG_ON(!mem->valid);
> > +}
> > +
> >  /*
> >   * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
> >   * limit reclaim to prevent infinite loops, if they ever occur.
> > @@ -1847,18 +1871,7 @@ static void mem_cgroup_cancel_charge(str
> >   * it's concern. (dropping refcnt from swap can be called against removed
> >   * memcg.)
> >   */
> > -static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
> > -{
> > -	struct cgroup_subsys_state *css;
> > 
> > -	/* ID 0 is unused ID */
> > -	if (!id)
> > -		return NULL;
> > -	css = css_lookup(&mem_cgroup_subsys, id);
> > -	if (!css)
> > -		return NULL;
> > -	return container_of(css, struct mem_cgroup, css);
> > -}
> > 
> >  struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
> >  {
> > @@ -1879,7 +1892,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr
> >  		ent.val = page_private(page);
> >  		id = lookup_swap_cgroup(ent);
> >  		rcu_read_lock();
> > -		mem = mem_cgroup_lookup(id);
> > +		mem = id_to_memcg(id);
> >  		if (mem && !css_tryget(&mem->css))
> >  			mem = NULL;
> >  		rcu_read_unlock();
> > @@ -2231,7 +2244,7 @@ __mem_cgroup_commit_charge_swapin(struct
> > 
> >  		id = swap_cgroup_record(ent, 0);
> >  		rcu_read_lock();
> > -		memcg = mem_cgroup_lookup(id);
> > +		memcg = id_to_memcg(id);
> >  		if (memcg) {
> >  			/*
> >  			 * This recorded memcg can be obsolete one. So, avoid
> > @@ -2240,9 +2253,10 @@ __mem_cgroup_commit_charge_swapin(struct
> >  			if (!mem_cgroup_is_root(memcg))
> >  				res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
> >  			mem_cgroup_swap_statistics(memcg, false);
> > +			rcu_read_unlock();
> >  			mem_cgroup_put(memcg);
> > -		}
> > -		rcu_read_unlock();
> > +		} else
> > +			rcu_read_unlock();
> >  	}
> >  	/*
> >  	 * At swapin, we may charge account against cgroup which has no tasks.
> > @@ -2495,7 +2509,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
> > 
> >  	id = swap_cgroup_record(ent, 0);
> >  	rcu_read_lock();
> > -	memcg = mem_cgroup_lookup(id);
> > +	memcg = id_to_memcg(id);
> >  	if (memcg) {
> >  		/*
> >  		 * We uncharge this because swap is freed.
> > @@ -2504,9 +2518,10 @@ void mem_cgroup_uncharge_swap(swp_entry_
> >  		if (!mem_cgroup_is_root(memcg))
> >  			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
> >  		mem_cgroup_swap_statistics(memcg, false);
> > +		rcu_read_unlock();
> >  		mem_cgroup_put(memcg);
> > -	}
> > -	rcu_read_unlock();
> > +	} else
> > +		rcu_read_unlock();
> >  }
> > 
> >  /**
> > @@ -4010,6 +4025,9 @@ static struct mem_cgroup *mem_cgroup_all
> >  	struct mem_cgroup *mem;
> >  	int size = sizeof(struct mem_cgroup);
> > 
> > +	if (atomic_read(&mem_cgroup_num) == NR_MEMCG_GROUPS)
> > +		return NULL;
> > +
> >  	/* Can be very big if MAX_NUMNODES is very big */
> >  	if (size < PAGE_SIZE)
> >  		mem = kmalloc(size, GFP_KERNEL);
> > @@ -4020,6 +4038,7 @@ static struct mem_cgroup *mem_cgroup_all
> >  		return NULL;
> > 
> >  	memset(mem, 0, size);
> > +	mem->valid = 1;
> >  	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
> >  	if (!mem->stat) {
> >  		if (size < PAGE_SIZE)
> > @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
> >  	mem_cgroup_remove_from_trees(mem);
> >  	free_css_id(&mem_cgroup_subsys, &mem->css);
> > 
> > +	atomic_dec(&mem_cgroup_num);
> >  	for_each_node_state(node, N_POSSIBLE)
> >  		free_mem_cgroup_per_zone_info(mem, node);
> > 
> > @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
> >  		vfree(mem);
> >  }
> > 
> > +static void mem_cgroup_free(struct mem_cgroup *mem)
> > +{
> > +	/* No more lookup */
> > +	mem->valid = 0;
> > +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> > +	/*
> > +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> > + 	 * call_rcu();
> > + 	 */
> > +	synchronize_rcu();
> > +	__mem_cgroup_free(mem);
> > +}
> > +
> >  static void mem_cgroup_get(struct mem_cgroup *mem)
> >  {
> >  	atomic_inc(&mem->refcnt);
> > @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
> >  {
> >  	if (atomic_sub_and_test(count, &mem->refcnt)) {
> >  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> > -		__mem_cgroup_free(mem);
> > +		mem_cgroup_free(mem);
> >  		if (parent)
> >  			mem_cgroup_put(parent);
> >  	}
> > @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
> >  	atomic_set(&mem->refcnt, 1);
> >  	mem->move_charge_at_immigrate = 0;
> >  	mutex_init(&mem->thresholds_lock);
> > +	atomic_inc(&mem_cgroup_num);
> > +	register_memcg_id(mem);
> >  	return &mem->css;
> >  free_out:
> > -	__mem_cgroup_free(mem);
> > +	mem_cgroup_free(mem);
> >  	root_mem_cgroup = NULL;
> >  	return ERR_PTR(error);
> >  }
> > Index: mmotm-0811/init/Kconfig
> > ===================================================================
> > --- mmotm-0811.orig/init/Kconfig
> > +++ mmotm-0811/init/Kconfig
> > @@ -594,6 +594,16 @@ config CGROUP_MEM_RES_CTLR_SWAP
> >  	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
> >  	  size is 4096bytes, 512k per 1Gbytes of swap.
> > 
> > +config MEM_CGROUP_MAX_GROUPS
> > +	int "Maximum number of memory cgroups on a system"
> > +	range 1 65535
> > +	default 8192 if 64BIT
> > +	default 2048 if 32BIT
> > +	help
> > +	  Memory cgroup has limitation of the number of groups created.
> > +	  Please select your favorite value. The more you allow, the more
> > +	  memory(a pointer per group) will be consumed.
> > +
> 
> Looks good, quick thought - should we expost memcg->id to user space
> through a config file? I don't see any reason at this point, unless we
> do it for all controllers.
> 

I wonder....showing whether 2 interfaces as "path name" and "id" to users is a
good thing or not. Yes, it's convenient to developpers as me and you, others,
but I don't think it's useful to users, novice people.

I'd like to avoid showing show memcg->id to users as much as possible. I don't
want to say but memcg is enough complicated.


Thanks,
-Kame

Re: [PATCH 2/5] memcg: quick memcg lookup array

[KAMEZAWA Hiroyuki]

On Tue, 31 Aug 2010 12:44:14 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-08-25 17:07:41]:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > Now, memory cgroup has an ID per cgroup and make use of it at
> >  - hierarchy walk,
> >  - swap recording.
> > 
> > This patch is for making more use of it. The final purpose is
> > to replace page_cgroup->mem_cgroup's pointer to an unsigned short.
> > 
> > This patch caches a pointer of memcg in an array. By this, we
> > don't have to call css_lookup() which requires radix-hash walk.
> > This saves some amount of memory footprint at lookup memcg via id.
> > 
> > Changelog: 20100825
> >  - applied comments.
> > 
> > Changelog: 20100811
> >  - adjusted onto mmotm-2010-08-11
> >  - fixed RCU related parts.
> >  - use attach_id() callback.
> > 
> > Changelog: 20100804
> >  - fixed description in init/Kconfig
> > 
> > Changelog: 20100730
> >  - fixed rcu_read_unlock() placement.
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  init/Kconfig    |   10 +++++++
> >  mm/memcontrol.c |   75 +++++++++++++++++++++++++++++++++++++++++---------------
> >  2 files changed, 65 insertions(+), 20 deletions(-)
> > 
> > Index: mmotm-0811/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0811.orig/mm/memcontrol.c
> > +++ mmotm-0811/mm/memcontrol.c
> > @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
> >   */
> >  struct mem_cgroup {
> >  	struct cgroup_subsys_state css;
> > +	int	valid; /* for checking validness under RCU access.*/
> >  	/*
> >  	 * the counter to account for memory usage
> >  	 */
> > @@ -294,6 +295,29 @@ static bool move_file(void)
> >  					&mc.to->move_charge_at_immigrate);
> >  }
> > 
> > +/* 0 is unused */
> > +static atomic_t mem_cgroup_num;
> > +#define NR_MEMCG_GROUPS (CONFIG_MEM_CGROUP_MAX_GROUPS + 1)
> > +static struct mem_cgroup *mem_cgroups[NR_MEMCG_GROUPS] __read_mostly;
> > +
> > +/* Must be called under rcu_read_lock */
> > +static struct mem_cgroup *id_to_memcg(unsigned short id)
> > +{
> > +	struct mem_cgroup *mem;
> > +	/* see mem_cgroup_free() */
> > +	mem = rcu_dereference_check(mem_cgroups[id], rcu_read_lock_held());
> > +	if (likely(mem && mem->valid))
> > +		return mem;
> > +	return NULL;
> > +}
> > +
> > +static void register_memcg_id(struct mem_cgroup *mem)
> > +{
> > +	int id = css_id(&mem->css);
> > +	rcu_assign_pointer(mem_cgroups[id], mem);
> > +	VM_BUG_ON(!mem->valid);
> > +}
> > +
> >  /*
> >   * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
> >   * limit reclaim to prevent infinite loops, if they ever occur.
> > @@ -1847,18 +1871,7 @@ static void mem_cgroup_cancel_charge(str
> >   * it's concern. (dropping refcnt from swap can be called against removed
> >   * memcg.)
> >   */
> > -static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
> > -{
> > -	struct cgroup_subsys_state *css;
> > 
> > -	/* ID 0 is unused ID */
> > -	if (!id)
> > -		return NULL;
> > -	css = css_lookup(&mem_cgroup_subsys, id);
> > -	if (!css)
> > -		return NULL;
> > -	return container_of(css, struct mem_cgroup, css);
> > -}
> > 
> >  struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
> >  {
> > @@ -1879,7 +1892,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr
> >  		ent.val = page_private(page);
> >  		id = lookup_swap_cgroup(ent);
> >  		rcu_read_lock();
> > -		mem = mem_cgroup_lookup(id);
> > +		mem = id_to_memcg(id);
> >  		if (mem && !css_tryget(&mem->css))
> >  			mem = NULL;
> >  		rcu_read_unlock();
> > @@ -2231,7 +2244,7 @@ __mem_cgroup_commit_charge_swapin(struct
> > 
> >  		id = swap_cgroup_record(ent, 0);
> >  		rcu_read_lock();
> > -		memcg = mem_cgroup_lookup(id);
> > +		memcg = id_to_memcg(id);
> >  		if (memcg) {
> >  			/*
> >  			 * This recorded memcg can be obsolete one. So, avoid
> > @@ -2240,9 +2253,10 @@ __mem_cgroup_commit_charge_swapin(struct
> >  			if (!mem_cgroup_is_root(memcg))
> >  				res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
> >  			mem_cgroup_swap_statistics(memcg, false);
> > +			rcu_read_unlock();
> >  			mem_cgroup_put(memcg);
> > -		}
> > -		rcu_read_unlock();
> > +		} else
> > +			rcu_read_unlock();
> >  	}
> >  	/*
> >  	 * At swapin, we may charge account against cgroup which has no tasks.
> > @@ -2495,7 +2509,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
> > 
> >  	id = swap_cgroup_record(ent, 0);
> >  	rcu_read_lock();
> > -	memcg = mem_cgroup_lookup(id);
> > +	memcg = id_to_memcg(id);
> >  	if (memcg) {
> >  		/*
> >  		 * We uncharge this because swap is freed.
> > @@ -2504,9 +2518,10 @@ void mem_cgroup_uncharge_swap(swp_entry_
> >  		if (!mem_cgroup_is_root(memcg))
> >  			res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
> >  		mem_cgroup_swap_statistics(memcg, false);
> > +		rcu_read_unlock();
> >  		mem_cgroup_put(memcg);
> > -	}
> > -	rcu_read_unlock();
> > +	} else
> > +		rcu_read_unlock();
> >  }
> > 
> >  /**
> > @@ -4010,6 +4025,9 @@ static struct mem_cgroup *mem_cgroup_all
> >  	struct mem_cgroup *mem;
> >  	int size = sizeof(struct mem_cgroup);
> > 
> > +	if (atomic_read(&mem_cgroup_num) == NR_MEMCG_GROUPS)
> > +		return NULL;
> > +
> >  	/* Can be very big if MAX_NUMNODES is very big */
> >  	if (size < PAGE_SIZE)
> >  		mem = kmalloc(size, GFP_KERNEL);
> > @@ -4020,6 +4038,7 @@ static struct mem_cgroup *mem_cgroup_all
> >  		return NULL;
> > 
> >  	memset(mem, 0, size);
> > +	mem->valid = 1;
> >  	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
> >  	if (!mem->stat) {
> >  		if (size < PAGE_SIZE)
> > @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
> >  	mem_cgroup_remove_from_trees(mem);
> >  	free_css_id(&mem_cgroup_subsys, &mem->css);
> > 
> > +	atomic_dec(&mem_cgroup_num);
> >  	for_each_node_state(node, N_POSSIBLE)
> >  		free_mem_cgroup_per_zone_info(mem, node);
> > 
> > @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
> >  		vfree(mem);
> >  }
> > 
> > +static void mem_cgroup_free(struct mem_cgroup *mem)
> > +{
> > +	/* No more lookup */
> > +	mem->valid = 0;
> > +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> > +	/*
> > +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> > + 	 * call_rcu();
> > + 	 */
> > +	synchronize_rcu();
> > +	__mem_cgroup_free(mem);
> > +}
> > +
> >  static void mem_cgroup_get(struct mem_cgroup *mem)
> >  {
> >  	atomic_inc(&mem->refcnt);
> > @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
> >  {
> >  	if (atomic_sub_and_test(count, &mem->refcnt)) {
> >  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> > -		__mem_cgroup_free(mem);
> > +		mem_cgroup_free(mem);
> >  		if (parent)
> >  			mem_cgroup_put(parent);
> >  	}
> > @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
> >  	atomic_set(&mem->refcnt, 1);
> >  	mem->move_charge_at_immigrate = 0;
> >  	mutex_init(&mem->thresholds_lock);
> > +	atomic_inc(&mem_cgroup_num);
> > +	register_memcg_id(mem);
> >  	return &mem->css;
> >  free_out:
> > -	__mem_cgroup_free(mem);
> > +	mem_cgroup_free(mem);
> >  	root_mem_cgroup = NULL;
> >  	return ERR_PTR(error);
> >  }
> > Index: mmotm-0811/init/Kconfig
> > ===================================================================
> > --- mmotm-0811.orig/init/Kconfig
> > +++ mmotm-0811/init/Kconfig
> > @@ -594,6 +594,16 @@ config CGROUP_MEM_RES_CTLR_SWAP
> >  	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
> >  	  size is 4096bytes, 512k per 1Gbytes of swap.
> > 
> > +config MEM_CGROUP_MAX_GROUPS
> > +	int "Maximum number of memory cgroups on a system"
> > +	range 1 65535
> > +	default 8192 if 64BIT
> > +	default 2048 if 32BIT
> > +	help
> > +	  Memory cgroup has limitation of the number of groups created.
> > +	  Please select your favorite value. The more you allow, the more
> > +	  memory(a pointer per group) will be consumed.
> > +
> 
> Looks good, quick thought - should we expost memcg->id to user space
> through a config file? I don't see any reason at this point, unless we
> do it for all controllers.
> 

I wonder....showing whether 2 interfaces as "path name" and "id" to users is a
good thing or not. Yes, it's convenient to developpers as me and you, others,
but I don't think it's useful to users, novice people.

I'd like to avoid showing show memcg->id to users as much as possible. I don't
want to say but memcg is enough complicated.


Thanks,
-Kame


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Re: [PATCH 2/5] memcg: quick memcg lookup array

[KAMEZAWA Hiroyuki]

On Mon, 30 Aug 2010 17:03:24 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> > Index: mmotm-0811/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0811.orig/mm/memcontrol.c
> > +++ mmotm-0811/mm/memcontrol.c
> > @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
> >   */
> >  struct mem_cgroup {
> >  	struct cgroup_subsys_state css;
> > +	int	valid; /* for checking validness under RCU access.*/
> >  	/*
> >  	 * the counter to account for memory usage
> >  	 */
> Do we really need to add this new member ?
> Can't we safely access "mem(=rcu_dereference(mem_cgroup[id]))" under rcu_read_lock() ?
> (iow, "mem" is not freed ?)
> 

Maybe this can be removed. I'll check again.




> 
> > @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
> >  	mem_cgroup_remove_from_trees(mem);
> >  	free_css_id(&mem_cgroup_subsys, &mem->css);
> >  
> > +	atomic_dec(&mem_cgroup_num);
> >  	for_each_node_state(node, N_POSSIBLE)
> >  		free_mem_cgroup_per_zone_info(mem, node);
> >  
> > @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
> >  		vfree(mem);
> >  }
> >  
> > +static void mem_cgroup_free(struct mem_cgroup *mem)
> > +{
> > +	/* No more lookup */
> > +	mem->valid = 0;
> > +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> > +	/*
> > +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> > + 	 * call_rcu();
> > + 	 */
> > +	synchronize_rcu();
> > +	__mem_cgroup_free(mem);
> > +}
> > +
> >  static void mem_cgroup_get(struct mem_cgroup *mem)
> >  {
> >  	atomic_inc(&mem->refcnt);
> > @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
> >  {
> >  	if (atomic_sub_and_test(count, &mem->refcnt)) {
> >  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> > -		__mem_cgroup_free(mem);
> > +		mem_cgroup_free(mem);
> >  		if (parent)
> >  			mem_cgroup_put(parent);
> >  	}
> > @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
> >  	atomic_set(&mem->refcnt, 1);
> >  	mem->move_charge_at_immigrate = 0;
> >  	mutex_init(&mem->thresholds_lock);
> > +	atomic_inc(&mem_cgroup_num);
> > +	register_memcg_id(mem);
> >  	return &mem->css;
> >  free_out:
> > -	__mem_cgroup_free(mem);
> > +	mem_cgroup_free(mem);
> >  	root_mem_cgroup = NULL;
> >  	return ERR_PTR(error);
> >  }
> I think mem_cgroup_num should be increased at mem_cgroup_alloc(), because it
> is decreased at __mem_cgroup_free(). Otherwise, it can be decreased while it
> has not been increased, if mem_cgroup_create() fails after mem_cgroup_alloc().
> 

Hmm. thank you for checking, I'll fix.

Thanks,
-Kame

Re: [PATCH 2/5] memcg: quick memcg lookup array

[KAMEZAWA Hiroyuki]

On Mon, 30 Aug 2010 17:03:24 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> > Index: mmotm-0811/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0811.orig/mm/memcontrol.c
> > +++ mmotm-0811/mm/memcontrol.c
> > @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
> >   */
> >  struct mem_cgroup {
> >  	struct cgroup_subsys_state css;
> > +	int	valid; /* for checking validness under RCU access.*/
> >  	/*
> >  	 * the counter to account for memory usage
> >  	 */
> Do we really need to add this new member ?
> Can't we safely access "mem(=rcu_dereference(mem_cgroup[id]))" under rcu_read_lock() ?
> (iow, "mem" is not freed ?)
> 

Maybe this can be removed. I'll check again.




> 
> > @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
> >  	mem_cgroup_remove_from_trees(mem);
> >  	free_css_id(&mem_cgroup_subsys, &mem->css);
> >  
> > +	atomic_dec(&mem_cgroup_num);
> >  	for_each_node_state(node, N_POSSIBLE)
> >  		free_mem_cgroup_per_zone_info(mem, node);
> >  
> > @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
> >  		vfree(mem);
> >  }
> >  
> > +static void mem_cgroup_free(struct mem_cgroup *mem)
> > +{
> > +	/* No more lookup */
> > +	mem->valid = 0;
> > +	rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> > +	/*
> > +	 * Because we call vfree() etc...use synchronize_rcu() rather than
> > + 	 * call_rcu();
> > + 	 */
> > +	synchronize_rcu();
> > +	__mem_cgroup_free(mem);
> > +}
> > +
> >  static void mem_cgroup_get(struct mem_cgroup *mem)
> >  {
> >  	atomic_inc(&mem->refcnt);
> > @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
> >  {
> >  	if (atomic_sub_and_test(count, &mem->refcnt)) {
> >  		struct mem_cgroup *parent = parent_mem_cgroup(mem);
> > -		__mem_cgroup_free(mem);
> > +		mem_cgroup_free(mem);
> >  		if (parent)
> >  			mem_cgroup_put(parent);
> >  	}
> > @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
> >  	atomic_set(&mem->refcnt, 1);
> >  	mem->move_charge_at_immigrate = 0;
> >  	mutex_init(&mem->thresholds_lock);
> > +	atomic_inc(&mem_cgroup_num);
> > +	register_memcg_id(mem);
> >  	return &mem->css;
> >  free_out:
> > -	__mem_cgroup_free(mem);
> > +	mem_cgroup_free(mem);
> >  	root_mem_cgroup = NULL;
> >  	return ERR_PTR(error);
> >  }
> I think mem_cgroup_num should be increased at mem_cgroup_alloc(), because it
> is decreased at __mem_cgroup_free(). Otherwise, it can be decreased while it
> has not been increased, if mem_cgroup_create() fails after mem_cgroup_alloc().
> 

Hmm. thank you for checking, I'll fix.

Thanks,
-Kame

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Re: [PATCH 4/5] memcg: lockless update of file stat with move-account safe method

[KAMEZAWA Hiroyuki]

On Tue, 31 Aug 2010 12:51:18 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Wed, 25 Aug 2010 17:10:50 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > At accounting file events per memory cgroup, we need to find memory cgroup
> > via page_cgroup->mem_cgroup. Now, we use lock_page_cgroup().
> > 
> > But, considering the context which page-cgroup for files are accessed,
> > we can use alternative light-weight mutual execusion in the most case.
> > At handling file-caches, the only race we have to take care of is "moving"
> > account, IOW, overwriting page_cgroup->mem_cgroup. Because file status
> > update is done while the page-cache is in stable state, we don't have to
> > take care of race with charge/uncharge.
> > 
> > Unlike charge/uncharge, "move" happens not so frequently. It happens only when
> > rmdir() and task-moving (with a special settings.)
> > This patch adds a race-checker for file-cache-status accounting v.s. account
> > moving. The new per-cpu-per-memcg counter MEM_CGROUP_ON_MOVE is added.
> > The routine for account move 
> >   1. Increment it before start moving
> >   2. Call synchronize_rcu()
> >   3. Decrement it after the end of moving.
> > By this, file-status-counting routine can check it needs to call
> > lock_page_cgroup(). In most case, I doesn't need to call it.
> > 
> > Changelog: 20100825
> >  - added a comment about mc.lock
> >  - fixed bad lock.
> > Changelog: 20100804
> >  - added a comment for possible optimization hint.
> > Changelog: 20100730
> >  - some cleanup.
> > Changelog: 20100729
> >  - replaced __this_cpu_xxx() with this_cpu_xxx
> >    (because we don't call spinlock)
> >  - added VM_BUG_ON().
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> (snip)
> 
> > @@ -1505,29 +1551,36 @@ void mem_cgroup_update_file_mapped(struc
> >  {
> >  	struct mem_cgroup *mem;
> >  	struct page_cgroup *pc;
> > +	bool need_lock = false;
> >  
> >  	pc = lookup_page_cgroup(page);
> >  	if (unlikely(!pc))
> >  		return;
> > -
> > -	lock_page_cgroup(pc);
> > +	rcu_read_lock();
> >  	mem = id_to_memcg(pc->mem_cgroup, true);
> It doesn't cause any problem, but I think it would be better to change this to
> "id_to_memcg(..., false)". It's just under rcu_read_lock(), not under page_cgroup
> lock anymore.
> 
ok, I'll apply your suggestion.

> Otherwise, it looks good to me.
> 
> Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> 

Thanks!
-Kame

Re: [PATCH 4/5] memcg: lockless update of file stat with move-account safe method

[KAMEZAWA Hiroyuki]

On Tue, 31 Aug 2010 12:51:18 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Wed, 25 Aug 2010 17:10:50 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > At accounting file events per memory cgroup, we need to find memory cgroup
> > via page_cgroup->mem_cgroup. Now, we use lock_page_cgroup().
> > 
> > But, considering the context which page-cgroup for files are accessed,
> > we can use alternative light-weight mutual execusion in the most case.
> > At handling file-caches, the only race we have to take care of is "moving"
> > account, IOW, overwriting page_cgroup->mem_cgroup. Because file status
> > update is done while the page-cache is in stable state, we don't have to
> > take care of race with charge/uncharge.
> > 
> > Unlike charge/uncharge, "move" happens not so frequently. It happens only when
> > rmdir() and task-moving (with a special settings.)
> > This patch adds a race-checker for file-cache-status accounting v.s. account
> > moving. The new per-cpu-per-memcg counter MEM_CGROUP_ON_MOVE is added.
> > The routine for account move 
> >   1. Increment it before start moving
> >   2. Call synchronize_rcu()
> >   3. Decrement it after the end of moving.
> > By this, file-status-counting routine can check it needs to call
> > lock_page_cgroup(). In most case, I doesn't need to call it.
> > 
> > Changelog: 20100825
> >  - added a comment about mc.lock
> >  - fixed bad lock.
> > Changelog: 20100804
> >  - added a comment for possible optimization hint.
> > Changelog: 20100730
> >  - some cleanup.
> > Changelog: 20100729
> >  - replaced __this_cpu_xxx() with this_cpu_xxx
> >    (because we don't call spinlock)
> >  - added VM_BUG_ON().
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> (snip)
> 
> > @@ -1505,29 +1551,36 @@ void mem_cgroup_update_file_mapped(struc
> >  {
> >  	struct mem_cgroup *mem;
> >  	struct page_cgroup *pc;
> > +	bool need_lock = false;
> >  
> >  	pc = lookup_page_cgroup(page);
> >  	if (unlikely(!pc))
> >  		return;
> > -
> > -	lock_page_cgroup(pc);
> > +	rcu_read_lock();
> >  	mem = id_to_memcg(pc->mem_cgroup, true);
> It doesn't cause any problem, but I think it would be better to change this to
> "id_to_memcg(..., false)". It's just under rcu_read_lock(), not under page_cgroup
> lock anymore.
> 
ok, I'll apply your suggestion.

> Otherwise, it looks good to me.
> 
> Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> 

Thanks!
-Kame

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Re: [PATCH 5/5] memcg: generic file stat accounting interface

[KAMEZAWA Hiroyuki]

On Tue, 31 Aug 2010 13:33:29 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Wed, 25 Aug 2010 17:11:40 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > Preparing for adding new status arounf file caches.(dirty, writeback,etc..)
> > Using a unified macro and more generic names.
> > All counters will have the same rule for updating.
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> 
> one nitpick.
> 
> > @@ -2042,17 +2031,20 @@ static void __mem_cgroup_commit_charge(s
> >  static void __mem_cgroup_move_account(struct page_cgroup *pc,
> >  	struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
> >  {
> > +	int i;
> >  	VM_BUG_ON(from == to);
> >  	VM_BUG_ON(PageLRU(pc->page));
> >  	VM_BUG_ON(!PageCgroupLocked(pc));
> >  	VM_BUG_ON(!PageCgroupUsed(pc));
> >  	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
> >  
> > -	if (PageCgroupFileMapped(pc)) {
> > +	for (i = MEM_CGROUP_FSTAT_BASE; i < MEM_CGROUP_FSTAT_END; ++i) {
> > +		if (!test_bit(fflag_idx(MEMCG_FSTAT_IDX(i)), &pc->flags))
> > +			continue;
> >  		/* Update mapped_file data for mem_cgroup */
> It might be better to update this comment too.
> 
> 	/* Update file-stat data for mem_cgroup */
> 
> or something ?
> 
Nice catch. I'll fix this.

-Kame

Re: [PATCH 5/5] memcg: generic file stat accounting interface

[KAMEZAWA Hiroyuki]

On Tue, 31 Aug 2010 13:33:29 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Wed, 25 Aug 2010 17:11:40 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > Preparing for adding new status arounf file caches.(dirty, writeback,etc..)
> > Using a unified macro and more generic names.
> > All counters will have the same rule for updating.
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> 
> one nitpick.
> 
> > @@ -2042,17 +2031,20 @@ static void __mem_cgroup_commit_charge(s
> >  static void __mem_cgroup_move_account(struct page_cgroup *pc,
> >  	struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
> >  {
> > +	int i;
> >  	VM_BUG_ON(from == to);
> >  	VM_BUG_ON(PageLRU(pc->page));
> >  	VM_BUG_ON(!PageCgroupLocked(pc));
> >  	VM_BUG_ON(!PageCgroupUsed(pc));
> >  	VM_BUG_ON(id_to_memcg(pc->mem_cgroup, true) != from);
> >  
> > -	if (PageCgroupFileMapped(pc)) {
> > +	for (i = MEM_CGROUP_FSTAT_BASE; i < MEM_CGROUP_FSTAT_END; ++i) {
> > +		if (!test_bit(fflag_idx(MEMCG_FSTAT_IDX(i)), &pc->flags))
> > +			continue;
> >  		/* Update mapped_file data for mem_cgroup */
> It might be better to update this comment too.
> 
> 	/* Update file-stat data for mem_cgroup */
> 
> or something ?
> 
Nice catch. I'll fix this.

-Kame

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