[RFC PATCH v3 5/8] mm: extend working set reporting to memcgs

[Yuanchu Xie <yuanchu@google.com>]

Break down the system-wide working set reporting into
per-memcg reports, which aggregages its children hierarchically.
The per-node working set reporting histograms and refresh/report
threshold files are presented as memcg files, showing a report
containing all the nodes.

Memcg interface:
/sys/fs/cgroup/.../memory.workingset.page_age
	The memcg equivalent of the sysfs workingset page age histogram,
	breaks down the workingset of this memcg and its children into
	page age intervals. Each node is prefixed with a node header and
	a newline. Non-proactive direct reclaim on this memcg can also
	wake up userspace agents that are waiting on this file.
	e.g.
	N0
	1000 anon=0 file=0
	2000 anon=0 file=0
	3000 anon=0 file=0
	4000 anon=0 file=0
	5000 anon=0 file=0
	18446744073709551615 anon=0 file=0

/sys/fs/cgroup/.../memory.workingset.page_age_intervals
	Configures the intervals for the page age histogram. This file
	operates on a per-node basis, allowing for different intervals
	for each node.
	e.g.
	echo N0=1000,2000,3000,4000,5000 > memory.workingset.page_age_intervals

/sys/fs/cgroup/.../memory.workingset.refresh_interval
	The memcg equivalent of the sysfs refresh interval. A per-node
	number of how much time a page age histogram is valid for, in
	milliseconds.
	e.g.
	echo N0=2000 > memory.workingset.refresh_interval

/sys/fs/cgroup/.../memory.workingset.report_threshold
	The memcg equivalent of the sysfs report threshold. A per-node
	number of how often userspace agent waiting on the page age
	histogram can be woken up, in milliseconds.
	e.g.
	echo N0=1000 > memory.workingset.report_threshold

Signed-off-by: Yuanchu Xie <yuanchu@google.com>
---
 include/linux/memcontrol.h        |   5 +
 include/linux/workingset_report.h |   6 +-
 mm/internal.h                     |   2 +
 mm/memcontrol.c                   | 267 +++++++++++++++++++++++++++++-
 mm/workingset_report.c            |  10 +-
 5 files changed, 286 insertions(+), 4 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 20ff87f8e001..7d7bc0928961 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -335,6 +335,11 @@ struct mem_cgroup {
 	struct lru_gen_mm_list mm_list;
 #endif
 
+#ifdef CONFIG_WORKINGSET_REPORT
+	/* memory.workingset.page_age file */
+	struct cgroup_file workingset_page_age_file;
+#endif
+
 	struct mem_cgroup_per_node *nodeinfo[];
 };
 
diff --git a/include/linux/workingset_report.h b/include/linux/workingset_report.h
index 589d240d6251..502542c812b3 100644
--- a/include/linux/workingset_report.h
+++ b/include/linux/workingset_report.h
@@ -9,6 +9,7 @@ struct mem_cgroup;
 struct pglist_data;
 struct node;
 struct lruvec;
+struct cgroup_file;
 
 #ifdef CONFIG_WORKINGSET_REPORT
 
@@ -38,7 +39,10 @@ struct wsr_state {
 	unsigned long report_threshold;
 	unsigned long refresh_interval;
 
-	struct kernfs_node *page_age_sys_file;
+	union {
+		struct kernfs_node *page_age_sys_file;
+		struct cgroup_file *page_age_cgroup_file;
+	};
 
 	/* breakdown of workingset by page age */
 	struct mutex page_age_lock;
diff --git a/mm/internal.h b/mm/internal.h
index 36480c7ac0dd..3730c8399ad4 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -212,6 +212,8 @@ extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason
 void notify_workingset(struct mem_cgroup *memcg, struct pglist_data *pgdat);
 /* Requires wsr->page_age_lock held */
 void wsr_refresh_scan(struct lruvec *lruvec, unsigned long refresh_interval);
+int workingset_report_intervals_parse(char *src,
+				      struct wsr_report_bins *bins);
 #else
 static inline void notify_workingset(struct mem_cgroup *memcg,
 				     struct pglist_data *pgdat)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2f07141de16c..75bda5f7994d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7005,6 +7005,245 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,
 	return nbytes;
 }
 
+#ifdef CONFIG_WORKINGSET_REPORT
+static int memory_ws_page_age_intervals_show(struct seq_file *m, void *v)
+{
+	int nid;
+	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+
+	for_each_node_state(nid, N_MEMORY) {
+		struct wsr_state *wsr;
+		struct wsr_page_age_histo *page_age;
+		int i, nr_bins;
+
+		wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+		mutex_lock(&wsr->page_age_lock);
+		page_age = wsr->page_age;
+		if (!page_age)
+			goto no_page_age;
+		seq_printf(m, "N%d=", nid);
+		nr_bins = page_age->bins.nr_bins;
+		for (i = 0; i < nr_bins; ++i) {
+			struct wsr_report_bin *bin =
+				&page_age->bins.bins[i];
+
+			seq_printf(m, "%u", jiffies_to_msecs(bin->idle_age));
+			if (i + 1 < nr_bins)
+				seq_putc(m, ',');
+		}
+		seq_putc(m, ' ');
+no_page_age:
+		mutex_unlock(&wsr->page_age_lock);
+	}
+	seq_putc(m, '\n');
+
+	return 0;
+}
+
+static ssize_t memory_wsr_interval_parse(struct kernfs_open_file *of, char *buf,
+					 size_t nbytes, unsigned int *nid_out,
+					 struct wsr_report_bins *bins)
+{
+	char *node, *intervals;
+	unsigned int nid;
+	int err;
+
+	buf = strstrip(buf);
+	intervals = buf;
+	node = strsep(&intervals, "=");
+
+	if (*node != 'N')
+		return -EINVAL;
+
+	err = kstrtouint(node + 1, 0, &nid);
+	if (err)
+		return err;
+
+	if (nid >= nr_node_ids || !node_state(nid, N_MEMORY))
+		return -EINVAL;
+
+	err = workingset_report_intervals_parse(intervals, bins);
+	if (err < 0)
+		return err;
+
+	*nid_out = nid;
+	return err;
+}
+
+static ssize_t memory_ws_page_age_intervals_write(struct kernfs_open_file *of,
+						  char *buf, size_t nbytes,
+						  loff_t off)
+{
+	unsigned int nid;
+	int err;
+	struct wsr_page_age_histo *page_age = NULL, *old;
+	struct wsr_state *wsr;
+	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+
+	page_age =
+		kzalloc(sizeof(struct wsr_page_age_histo), GFP_KERNEL_ACCOUNT);
+
+	if (!page_age) {
+		err = -ENOMEM;
+		goto failed;
+	}
+
+	err = memory_wsr_interval_parse(of, buf, nbytes, &nid, &page_age->bins);
+	if (err < 0)
+		goto failed;
+
+	if (err == 0) {
+		kfree(page_age);
+		page_age = NULL;
+	}
+
+	wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+	mutex_lock(&wsr->page_age_lock);
+	old = xchg(&wsr->page_age, page_age);
+	mutex_unlock(&wsr->page_age_lock);
+	kfree(old);
+	return nbytes;
+failed:
+	kfree(page_age);
+	return err;
+}
+
+static int memory_ws_refresh_interval_show(struct seq_file *m, void *v)
+{
+	int nid;
+	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+
+	for_each_node_state(nid, N_MEMORY) {
+		struct wsr_state *wsr =
+			&mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+
+		seq_printf(m, "N%d=%u ", nid,
+			   jiffies_to_msecs(READ_ONCE(wsr->refresh_interval)));
+	}
+	seq_putc(m, '\n');
+
+	return 0;
+}
+
+static ssize_t memory_wsr_threshold_parse(char *buf, size_t nbytes,
+					  unsigned int *nid_out,
+					  unsigned int *msecs)
+{
+	char *node, *threshold;
+	unsigned int nid;
+	int err;
+
+	buf = strstrip(buf);
+	threshold = buf;
+	node = strsep(&threshold, "=");
+
+	if (*node != 'N')
+		return -EINVAL;
+
+	err = kstrtouint(node + 1, 0, &nid);
+	if (err)
+		return err;
+
+	if (nid >= nr_node_ids || !node_state(nid, N_MEMORY))
+		return -EINVAL;
+
+	err = kstrtouint(threshold, 0, msecs);
+	if (err)
+		return err;
+
+	*nid_out = nid;
+
+	return nbytes;
+}
+
+static ssize_t memory_ws_refresh_interval_write(struct kernfs_open_file *of,
+						 char *buf, size_t nbytes,
+						 loff_t off)
+{
+	unsigned int nid, msecs;
+	struct wsr_state *wsr;
+	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+	ssize_t ret = memory_wsr_threshold_parse(buf, nbytes, &nid, &msecs);
+
+	if (ret < 0)
+		return ret;
+
+	wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+	WRITE_ONCE(wsr->refresh_interval, msecs_to_jiffies(msecs));
+	return ret;
+}
+
+static int memory_ws_report_threshold_show(struct seq_file *m, void *v)
+{
+	int nid;
+	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+
+	for_each_node_state(nid, N_MEMORY) {
+		struct wsr_state *wsr =
+			&mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+
+		seq_printf(m, "N%d=%u ", nid,
+			   jiffies_to_msecs(READ_ONCE(wsr->report_threshold)));
+	}
+	seq_putc(m, '\n');
+
+	return 0;
+}
+
+static ssize_t memory_ws_report_threshold_write(struct kernfs_open_file *of,
+						 char *buf, size_t nbytes,
+						 loff_t off)
+{
+	unsigned int nid, msecs;
+	struct wsr_state *wsr;
+	struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+	ssize_t ret = memory_wsr_threshold_parse(buf, nbytes, &nid, &msecs);
+
+	if (ret < 0)
+		return ret;
+
+	wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+	WRITE_ONCE(wsr->report_threshold, msecs_to_jiffies(msecs));
+	return ret;
+}
+
+static int memory_ws_page_age_show(struct seq_file *m, void *v)
+{
+	int nid;
+	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+
+	for_each_node_state(nid, N_MEMORY) {
+		struct wsr_state *wsr =
+			&mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr;
+		struct wsr_report_bin *bin;
+
+		if (!READ_ONCE(wsr->page_age))
+			continue;
+
+		wsr_refresh_report(wsr, memcg, NODE_DATA(nid));
+		mutex_lock(&wsr->page_age_lock);
+		if (!wsr->page_age)
+			goto unlock;
+		seq_printf(m, "N%d\n", nid);
+		for (bin = wsr->page_age->bins.bins;
+		     bin->idle_age != WORKINGSET_INTERVAL_MAX; bin++)
+			seq_printf(m, "%u anon=%lu file=%lu\n",
+				   jiffies_to_msecs(bin->idle_age),
+				   bin->nr_pages[0] * PAGE_SIZE,
+				   bin->nr_pages[1] * PAGE_SIZE);
+
+		seq_printf(m, "%lu anon=%lu file=%lu\n", WORKINGSET_INTERVAL_MAX,
+			   bin->nr_pages[0] * PAGE_SIZE,
+			   bin->nr_pages[1] * PAGE_SIZE);
+
+unlock:
+		mutex_unlock(&wsr->page_age_lock);
+	}
+
+	return 0;
+}
+#endif
+
 static struct cftype memory_files[] = {
 	{
 		.name = "current",
@@ -7073,7 +7312,33 @@ static struct cftype memory_files[] = {
 		.flags = CFTYPE_NS_DELEGATABLE,
 		.write = memory_reclaim,
 	},
-	{ }	/* terminate */
+#ifdef CONFIG_WORKINGSET_REPORT
+	{
+		.name = "workingset.page_age_intervals",
+		.flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE,
+		.seq_show = memory_ws_page_age_intervals_show,
+		.write = memory_ws_page_age_intervals_write,
+	},
+	{
+		.name = "workingset.refresh_interval",
+		.flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE,
+		.seq_show = memory_ws_refresh_interval_show,
+		.write = memory_ws_refresh_interval_write,
+	},
+	{
+		.name = "workingset.report_threshold",
+		.flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE,
+		.seq_show = memory_ws_report_threshold_show,
+		.write = memory_ws_report_threshold_write,
+	},
+	{
+		.name = "workingset.page_age",
+		.flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE,
+		.file_offset = offsetof(struct mem_cgroup, workingset_page_age_file),
+		.seq_show = memory_ws_page_age_show,
+	},
+#endif
+	{} /* terminate */
 };
 
 struct cgroup_subsys memory_cgrp_subsys = {
diff --git a/mm/workingset_report.c b/mm/workingset_report.c
index 3ed3b0e8f8ad..b00ffbfebcab 100644
--- a/mm/workingset_report.c
+++ b/mm/workingset_report.c
@@ -20,9 +20,12 @@
 void wsr_init(struct lruvec *lruvec)
 {
 	struct wsr_state *wsr = &lruvec->wsr;
+	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 
 	memset(wsr, 0, sizeof(*wsr));
 	mutex_init(&wsr->page_age_lock);
+	if (memcg && !mem_cgroup_is_root(memcg))
+		wsr->page_age_cgroup_file = &memcg->workingset_page_age_file;
 }
 
 void wsr_destroy(struct lruvec *lruvec)
@@ -34,7 +37,7 @@ void wsr_destroy(struct lruvec *lruvec)
 	memset(wsr, 0, sizeof(*wsr));
 }
 
-static int workingset_report_intervals_parse(char *src,
+int workingset_report_intervals_parse(char *src,
 				      struct wsr_report_bins *bins)
 {
 	int err = 0, i = 0;
@@ -490,5 +493,8 @@ void notify_workingset(struct mem_cgroup *memcg, struct pglist_data *pgdat)
 {
 	struct wsr_state *wsr = &mem_cgroup_lruvec(memcg, pgdat)->wsr;
 
-	kernfs_notify(wsr->page_age_sys_file);
+	if (mem_cgroup_is_root(memcg))
+		kernfs_notify(wsr->page_age_sys_file);
+	else
+		cgroup_file_notify(wsr->page_age_cgroup_file);
 }
-- 
2.44.0.396.g6e790dbe36-goog