memcg: add memory.vmscan_stat

The commit log of 0ae5e89c60c9 ("memcg: count the soft_limit reclaim
in...") says it adds scanning stats to memory.stat file.  But it doesn't
because we considered we needed to make a concensus for such new APIs.

This patch is a trial to add memory.scan_stat. This shows
  - the number of scanned pages(total, anon, file)
  - the number of rotated pages(total, anon, file)
  - the number of freed pages(total, anon, file)
  - the number of elaplsed time (including sleep/pause time)

  for both of direct/soft reclaim.

The biggest difference with oringinal Ying's one is that this file
can be reset by some write, as

  # echo 0 ...../memory.scan_stat

Example of output is here. This is a result after make -j 6 kernel
under 300M limit.

  [kamezawa@bluextal ~]$ cat /cgroup/memory/A/memory.scan_stat
  [kamezawa@bluextal ~]$ cat /cgroup/memory/A/memory.vmscan_stat
  scanned_pages_by_limit 9471864
  scanned_anon_pages_by_limit 6640629
  scanned_file_pages_by_limit 2831235
  rotated_pages_by_limit 4243974
  rotated_anon_pages_by_limit 3971968
  rotated_file_pages_by_limit 272006
  freed_pages_by_limit 2318492
  freed_anon_pages_by_limit 962052
  freed_file_pages_by_limit 1356440
  elapsed_ns_by_limit 351386416101
  scanned_pages_by_system 0
  scanned_anon_pages_by_system 0
  scanned_file_pages_by_system 0
  rotated_pages_by_system 0
  rotated_anon_pages_by_system 0
  rotated_file_pages_by_system 0
  freed_pages_by_system 0
  freed_anon_pages_by_system 0
  freed_file_pages_by_system 0
  elapsed_ns_by_system 0
  scanned_pages_by_limit_under_hierarchy 9471864
  scanned_anon_pages_by_limit_under_hierarchy 6640629
  scanned_file_pages_by_limit_under_hierarchy 2831235
  rotated_pages_by_limit_under_hierarchy 4243974
  rotated_anon_pages_by_limit_under_hierarchy 3971968
  rotated_file_pages_by_limit_under_hierarchy 272006
  freed_pages_by_limit_under_hierarchy 2318492
  freed_anon_pages_by_limit_under_hierarchy 962052
  freed_file_pages_by_limit_under_hierarchy 1356440
  elapsed_ns_by_limit_under_hierarchy 351386416101
  scanned_pages_by_system_under_hierarchy 0
  scanned_anon_pages_by_system_under_hierarchy 0
  scanned_file_pages_by_system_under_hierarchy 0
  rotated_pages_by_system_under_hierarchy 0
  rotated_anon_pages_by_system_under_hierarchy 0
  rotated_file_pages_by_system_under_hierarchy 0
  freed_pages_by_system_under_hierarchy 0
  freed_anon_pages_by_system_under_hierarchy 0
  freed_file_pages_by_system_under_hierarchy 0
  elapsed_ns_by_system_under_hierarchy 0

total_xxxx is for hierarchy management.

This will be useful for further memcg developments and need to be
developped before we do some complicated rework on LRU/softlimit
management.

This patch adds a new struct memcg_scanrecord into scan_control struct.
sc->nr_scanned at el is not designed for exporting information.  For
example, nr_scanned is reset frequentrly and incremented +2 at scanning
mapped pages.

To avoid complexity, I added a new param in scan_control which is for
exporting scanning score.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Ying Han <yinghan@google.com>
Cc: Andrew Bresticker <abrestic@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 166 insertions, 6 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dfeca594fd7a..04e505bfd7dd 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -205,6 +205,50 @@ struct mem_cgroup_eventfd_list {
 static void mem_cgroup_threshold(struct mem_cgroup *mem);
 static void mem_cgroup_oom_notify(struct mem_cgroup *mem);
 
+enum {
+	SCAN_BY_LIMIT,
+	SCAN_BY_SYSTEM,
+	NR_SCAN_CONTEXT,
+	SCAN_BY_SHRINK,	/* not recorded now */
+};
+
+enum {
+	SCAN,
+	SCAN_ANON,
+	SCAN_FILE,
+	ROTATE,
+	ROTATE_ANON,
+	ROTATE_FILE,
+	FREED,
+	FREED_ANON,
+	FREED_FILE,
+	ELAPSED,
+	NR_SCANSTATS,
+};
+
+struct scanstat {
+	spinlock_t	lock;
+	unsigned long	stats[NR_SCAN_CONTEXT][NR_SCANSTATS];
+	unsigned long	rootstats[NR_SCAN_CONTEXT][NR_SCANSTATS];
+};
+
+const char *scanstat_string[NR_SCANSTATS] = {
+	"scanned_pages",
+	"scanned_anon_pages",
+	"scanned_file_pages",
+	"rotated_pages",
+	"rotated_anon_pages",
+	"rotated_file_pages",
+	"freed_pages",
+	"freed_anon_pages",
+	"freed_file_pages",
+	"elapsed_ns",
+};
+#define SCANSTAT_WORD_LIMIT	"_by_limit"
+#define SCANSTAT_WORD_SYSTEM	"_by_system"
+#define SCANSTAT_WORD_HIERARCHY	"_under_hierarchy"
+
+
 /*
  * The memory controller data structure. The memory controller controls both
  * page cache and RSS per cgroup. We would eventually like to provide
@@ -270,7 +314,8 @@ struct mem_cgroup {
 
 	/* For oom notifier event fd */
 	struct list_head oom_notify;
-
+	/* For recording LRU-scan statistics */
+	struct scanstat scanstat;
 	/*
 	 * Should we move charges of a task when a task is moved into this
 	 * mem_cgroup ? And what type of charges should we move ?
@@ -1623,6 +1668,44 @@ bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
 }
 #endif
 
+static void __mem_cgroup_record_scanstat(unsigned long *stats,
+			   struct memcg_scanrecord *rec)
+{
+
+	stats[SCAN] += rec->nr_scanned[0] + rec->nr_scanned[1];
+	stats[SCAN_ANON] += rec->nr_scanned[0];
+	stats[SCAN_FILE] += rec->nr_scanned[1];
+
+	stats[ROTATE] += rec->nr_rotated[0] + rec->nr_rotated[1];
+	stats[ROTATE_ANON] += rec->nr_rotated[0];
+	stats[ROTATE_FILE] += rec->nr_rotated[1];
+
+	stats[FREED] += rec->nr_freed[0] + rec->nr_freed[1];
+	stats[FREED_ANON] += rec->nr_freed[0];
+	stats[FREED_FILE] += rec->nr_freed[1];
+
+	stats[ELAPSED] += rec->elapsed;
+}
+
+static void mem_cgroup_record_scanstat(struct memcg_scanrecord *rec)
+{
+	struct mem_cgroup *mem;
+	int context = rec->context;
+
+	if (context >= NR_SCAN_CONTEXT)
+		return;
+
+	mem = rec->mem;
+	spin_lock(&mem->scanstat.lock);
+	__mem_cgroup_record_scanstat(mem->scanstat.stats[context], rec);
+	spin_unlock(&mem->scanstat.lock);
+
+	mem = rec->root;
+	spin_lock(&mem->scanstat.lock);
+	__mem_cgroup_record_scanstat(mem->scanstat.rootstats[context], rec);
+	spin_unlock(&mem->scanstat.lock);
+}
+
 /*
  * Scan the hierarchy if needed to reclaim memory. We remember the last child
  * we reclaimed from, so that we don't end up penalizing one child extensively
@@ -1647,8 +1730,9 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 	bool noswap = reclaim_options & MEM_CGROUP_RECLAIM_NOSWAP;
 	bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;
 	bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;
+	struct memcg_scanrecord rec;
 	unsigned long excess;
-	unsigned long nr_scanned;
+	unsigned long scanned;
 
 	excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;
 
@@ -1656,6 +1740,15 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 	if (!check_soft && !shrink && root_mem->memsw_is_minimum)
 		noswap = true;
 
+	if (shrink)
+		rec.context = SCAN_BY_SHRINK;
+	else if (check_soft)
+		rec.context = SCAN_BY_SYSTEM;
+	else
+		rec.context = SCAN_BY_LIMIT;
+
+	rec.root = root_mem;
+
 	while (1) {
 		victim = mem_cgroup_select_victim(root_mem);
 		if (victim == root_mem) {
@@ -1696,14 +1789,23 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 			css_put(&victim->css);
 			continue;
 		}
+		rec.mem = victim;
+		rec.nr_scanned[0] = 0;
+		rec.nr_scanned[1] = 0;
+		rec.nr_rotated[0] = 0;
+		rec.nr_rotated[1] = 0;
+		rec.nr_freed[0] = 0;
+		rec.nr_freed[1] = 0;
+		rec.elapsed = 0;
 		/* we use swappiness of local cgroup */
 		if (check_soft) {
 			ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
-				noswap, zone, &nr_scanned);
-			*total_scanned += nr_scanned;
+				noswap, zone, &rec, &scanned);
+			*total_scanned += scanned;
 		} else
 			ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
-						noswap);
+						noswap, &rec);
+		mem_cgroup_record_scanstat(&rec);
 		css_put(&victim->css);
 		/*
 		 * At shrinking usage, we can't check we should stop here or
@@ -3792,14 +3894,18 @@ try_to_free:
 	/* try to free all pages in this cgroup */
 	shrink = 1;
 	while (nr_retries && mem->res.usage > 0) {
+		struct memcg_scanrecord rec;
 		int progress;
 
 		if (signal_pending(current)) {
 			ret = -EINTR;
 			goto out;
 		}
+		rec.context = SCAN_BY_SHRINK;
+		rec.mem = mem;
+		rec.root = mem;
 		progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL,
-						false);
+						false, &rec);
 		if (!progress) {
 			nr_retries--;
 			/* maybe some writeback is necessary */
@@ -4643,6 +4749,54 @@ static int mem_control_numa_stat_open(struct inode *unused, struct file *file)
 }
 #endif /* CONFIG_NUMA */
 
+static int mem_cgroup_vmscan_stat_read(struct cgroup *cgrp,
+				struct cftype *cft,
+				struct cgroup_map_cb *cb)
+{
+	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+	char string[64];
+	int i;
+
+	for (i = 0; i < NR_SCANSTATS; i++) {
+		strcpy(string, scanstat_string[i]);
+		strcat(string, SCANSTAT_WORD_LIMIT);
+		cb->fill(cb, string,  mem->scanstat.stats[SCAN_BY_LIMIT][i]);
+	}
+
+	for (i = 0; i < NR_SCANSTATS; i++) {
+		strcpy(string, scanstat_string[i]);
+		strcat(string, SCANSTAT_WORD_SYSTEM);
+		cb->fill(cb, string,  mem->scanstat.stats[SCAN_BY_SYSTEM][i]);
+	}
+
+	for (i = 0; i < NR_SCANSTATS; i++) {
+		strcpy(string, scanstat_string[i]);
+		strcat(string, SCANSTAT_WORD_LIMIT);
+		strcat(string, SCANSTAT_WORD_HIERARCHY);
+		cb->fill(cb, string,  mem->scanstat.rootstats[SCAN_BY_LIMIT][i]);
+	}
+	for (i = 0; i < NR_SCANSTATS; i++) {
+		strcpy(string, scanstat_string[i]);
+		strcat(string, SCANSTAT_WORD_SYSTEM);
+		strcat(string, SCANSTAT_WORD_HIERARCHY);
+		cb->fill(cb, string,  mem->scanstat.rootstats[SCAN_BY_SYSTEM][i]);
+	}
+	return 0;
+}
+
+static int mem_cgroup_reset_vmscan_stat(struct cgroup *cgrp,
+				unsigned int event)
+{
+	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+
+	spin_lock(&mem->scanstat.lock);
+	memset(&mem->scanstat.stats, 0, sizeof(mem->scanstat.stats));
+	memset(&mem->scanstat.rootstats, 0, sizeof(mem->scanstat.rootstats));
+	spin_unlock(&mem->scanstat.lock);
+	return 0;
+}
+
+
 static struct cftype mem_cgroup_files[] = {
 	{
 		.name = "usage_in_bytes",
@@ -4713,6 +4867,11 @@ static struct cftype mem_cgroup_files[] = {
 		.mode = S_IRUGO,
 	},
 #endif
+	{
+		.name = "vmscan_stat",
+		.read_map = mem_cgroup_vmscan_stat_read,
+		.trigger = mem_cgroup_reset_vmscan_stat,
+	},
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
@@ -4976,6 +5135,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 	atomic_set(&mem->refcnt, 1);
 	mem->move_charge_at_immigrate = 0;
 	mutex_init(&mem->thresholds_lock);
+	spin_lock_init(&mem->scanstat.lock);
 	return &mem->css;
 free_out:
 	__mem_cgroup_free(mem);