Add statistics account infrastructure for memory controller.

Changes from original:
 - divided into 2 patch (this one and show info)
 - changed from u64 to s64
 - added mem_cgroup_stat_add() and batched statistics modification logic.
 - removed stat init code because mem_cgroup is allocated by kzalloc().

Problem:
 - charge/uncharge count can be overflow. But they are unnecessary ?

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>

 mm/memcontrol.c |  120 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 116 insertions(+), 4 deletions(-)

Index: devel-2.6.23-rc8-mm2/mm/memcontrol.c
===================================================================
--- devel-2.6.23-rc8-mm2.orig/mm/memcontrol.c
+++ devel-2.6.23-rc8-mm2/mm/memcontrol.c
@@ -35,6 +35,63 @@ struct cgroup_subsys mem_cgroup_subsys;
 static const int MEM_CGROUP_RECLAIM_RETRIES = 5;
 
 /*
+ * Statistics for memory cgroup.
+ */
+enum mem_cgroup_stat_index {
+	/*
+	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
+	 */
+	MEM_CGROUP_STAT_PAGECACHE, /* # of pages charged as cache */
+	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as rss */
+
+	/*
+	 * usage = charge - uncharge.
+	 */
+	MEM_CGROUP_STAT_CHARGE,    /* # of pages charged */
+	MEM_CGROUP_STAT_UNCHARGE,  /* # of pages uncharged */
+
+	MEM_CGROUP_STAT_ACTIVE,	   /* # of pages in active list */
+	MEM_CGROUP_STAT_INACTIVE,  /* # of pages on inactive list */
+
+	MEM_CGROUP_STAT_NSTATS,
+};
+
+struct mem_cgroup_stat_cpu {
+	s64 count[MEM_CGROUP_STAT_NSTATS];
+} ____cacheline_aligned_in_smp;
+
+struct mem_cgroup_stat {
+	struct mem_cgroup_stat_cpu cpustat[NR_CPUS];
+};
+
+/*
+ * For batching....mem_cgroup_charge_statistics()(see below).
+ */
+static inline void mem_cgroup_stat_add(struct mem_cgroup_stat *stat,
+                enum mem_cgroup_stat_index idx, int val)
+{
+	int cpu = smp_processor_id();
+	stat->cpustat[cpu].count[idx] += val;
+}
+
+static inline void mem_cgroup_stat_inc(struct mem_cgroup_stat *stat,
+		enum mem_cgroup_stat_index idx)
+{
+	preempt_disable();
+	mem_cgroup_stat_add(stat, idx, 1);
+	preempt_enable();
+}
+
+static inline void mem_cgroup_stat_dec(struct mem_cgroup_stat *stat,
+		enum mem_cgroup_stat_index idx)
+{
+	preempt_disable();
+	mem_cgroup_stat_add(stat, idx, -1);
+	preempt_enable();
+}
+
+
+/*
  * The memory controller data structure. The memory controller controls both
  * page cache and RSS per cgroup. We would eventually like to provide
  * statistics based on the statistics developed by Rik Van Riel for clock-pro,
@@ -63,6 +120,10 @@ struct mem_cgroup {
 	 */
 	spinlock_t lru_lock;
 	unsigned long control_type;	/* control RSS or RSS+Pagecache */
+	/*
+	 * statistics.
+	 */
+	struct mem_cgroup_stat stat;
 };
 
 /*
@@ -96,6 +157,37 @@ enum {
 	MEM_CGROUP_TYPE_MAX,
 };
 
+/*
+ * Batched statistics modification.
+ * We have to modify several values at charge/uncharge..
+ */
+static inline void
+mem_cgroup_charge_statistics(struct mem_cgroup *mem, int flags, bool charge)
+{
+	int val = (charge)? 1 : -1;
+	preempt_disable();
+
+	if (flags & PCGF_PAGECACHE)
+		mem_cgroup_stat_add(&mem->stat, MEM_CGROUP_STAT_PAGECACHE, val);
+	else
+		mem_cgroup_stat_add(&mem->stat, MEM_CGROUP_STAT_RSS, val);
+
+	if (flags & PCGF_ACTIVE)
+		mem_cgroup_stat_add(&mem->stat, MEM_CGROUP_STAT_ACTIVE, val);
+	else
+		mem_cgroup_stat_add(&mem->stat, MEM_CGROUP_STAT_INACTIVE, val);
+
+	if(charge)
+		mem_cgroup_stat_add(&mem->stat, MEM_CGROUP_STAT_CHARGE, 1);
+	else
+		mem_cgroup_stat_add(&mem->stat, MEM_CGROUP_STAT_UNCHARGE, 1);
+
+	preempt_enable();
+}
+
+
+
+
 static struct mem_cgroup init_mem_cgroup;
 
 static inline
@@ -207,8 +299,23 @@ clear_page_cgroup(struct page *page, str
 }
 
 
-static void __mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
+static void __mem_cgroup_move_lists(struct page_cgroup *pc, bool active,
+				    struct mem_cgroup *mem)
 {
+	int moved = 0;
+
+	if (active && (pc->flags & PCGF_ACTIVE) == 0)
+		moved = 1; /* Move from inactive to active */
+	else if (!active && (pc->flags & PCGF_ACTIVE))
+		moved = -1; /* Move from active to inactive */
+
+	if (moved) {
+		struct mem_cgroup_stat *stat = &mem->stat;
+		preempt_disable();
+		mem_cgroup_stat_add(stat, MEM_CGROUP_STAT_ACTIVE, moved);
+		mem_cgroup_stat_add(stat, MEM_CGROUP_STAT_INACTIVE, -moved);
+		preempt_enable();
+	}
 	if (active) {
 		pc->flags |= PCGF_ACTIVE;
 		list_move(&pc->lru, &pc->mem_cgroup->active_list);
@@ -230,7 +337,7 @@ void mem_cgroup_move_lists(struct page_c
 	mem = pc->mem_cgroup;
 
 	spin_lock(&mem->lru_lock);
-	__mem_cgroup_move_lists(pc, active);
+	__mem_cgroup_move_lists(pc, active, mem);
 	spin_unlock(&mem->lru_lock);
 }
 
@@ -267,12 +374,12 @@ unsigned long mem_cgroup_isolate_pages(u
 		}
 
 		if (PageActive(page) && !active) {
-			__mem_cgroup_move_lists(pc, true);
+			__mem_cgroup_move_lists(pc, true, pc->mem_cgroup);
 			scan--;
 			continue;
 		}
 		if (!PageActive(page) && active) {
-			__mem_cgroup_move_lists(pc, false);
+			__mem_cgroup_move_lists(pc, false, pc->mem_cgroup);
 			scan--;
 			continue;
 		}
@@ -428,6 +535,9 @@ noreclaim:
 		goto retry;
 	}
 
+	/* Update statistics vector */
+	mem_cgroup_charge_statistics(mem, pc->flags, true);
+
 	spin_lock_irqsave(&mem->lru_lock, flags);
 	list_add(&pc->lru, &mem->active_list);
 	spin_unlock_irqrestore(&mem->lru_lock, flags);
@@ -494,6 +604,7 @@ void mem_cgroup_uncharge(struct page_cgr
 			spin_lock_irqsave(&mem->lru_lock, flags);
 			list_del_init(&pc->lru);
 			spin_unlock_irqrestore(&mem->lru_lock, flags);
+			mem_cgroup_charge_statistics(mem, pc->flags, false);
 			kfree(pc);
 		}
 	}
@@ -566,6 +677,7 @@ mem_cgroup_force_empty_list(struct mem_c
 			css_put(&mem->css);
 			res_counter_uncharge(&mem->res, PAGE_SIZE);
 			list_del_init(&pc->lru);
+			mem_cgroup_charge_statistics(mem, pc->flags, false);
 			kfree(pc);
 		} else
 			count = 1; /* being uncharged ? ...do relax */

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