[RFC][PATCH v7 07/14] memcg: add cgroupfs interface to memcg dirty limits

[Greg Thelen]

Add cgroupfs interface to memcg dirty page limits:
  Direct write-out is controlled with:
  - memory.dirty_ratio
  - memory.dirty_limit_in_bytes

  Background write-out is controlled with:
  - memory.dirty_background_ratio
  - memory.dirty_background_limit_bytes

Other memcg cgroupfs files support 'M', 'm', 'k', 'K', 'g'
and 'G' suffixes for byte counts.  This patch provides the
same functionality for memory.dirty_limit_in_bytes and
memory.dirty_background_limit_bytes.

Signed-off-by: Andrea Righi <arighi@xxxxxxxxxxx>
Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
Changelog since v3:
- Make use of new routine, __mem_cgroup_has_dirty_limit(), to disable memcg
  dirty limits when use_hierarchy=1.

Changelog since v1:
- Renamed newly created proc files:
  - memory.dirty_bytes -> memory.dirty_limit_in_bytes
  - memory.dirty_background_bytes -> memory.dirty_background_limit_in_bytes
- Allow [kKmMgG] suffixes for newly created dirty limit value cgroupfs files.

 mm/memcontrol.c |  114 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 114 insertions(+), 0 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f496677..248396c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -126,6 +126,13 @@ enum mem_cgroup_events_target {
 #define THRESHOLDS_EVENTS_TARGET (128)
 #define SOFTLIMIT_EVENTS_TARGET (1024)
 
+enum {
+	MEM_CGROUP_DIRTY_RATIO,
+	MEM_CGROUP_DIRTY_LIMIT_IN_BYTES,
+	MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
+	MEM_CGROUP_DIRTY_BACKGROUND_LIMIT_IN_BYTES,
+};
+
 struct mem_cgroup_stat_cpu {
 	long count[MEM_CGROUP_STAT_NSTATS];
 	unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
@@ -4638,6 +4645,89 @@ static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
 	return 0;
 }
 
+static u64 mem_cgroup_dirty_read(struct cgroup *cgrp, struct cftype *cft)
+{
+	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+	bool use_sys = !mem_cgroup_has_dirty_limit(mem);
+
+	switch (cft->private) {
+	case MEM_CGROUP_DIRTY_RATIO:
+		return use_sys ? vm_dirty_ratio : mem->dirty_param.dirty_ratio;
+	case MEM_CGROUP_DIRTY_LIMIT_IN_BYTES:
+		return use_sys ? vm_dirty_bytes : mem->dirty_param.dirty_bytes;
+	case MEM_CGROUP_DIRTY_BACKGROUND_RATIO:
+		return use_sys ? dirty_background_ratio :
+			mem->dirty_param.dirty_background_ratio;
+	case MEM_CGROUP_DIRTY_BACKGROUND_LIMIT_IN_BYTES:
+		return use_sys ? dirty_background_bytes :
+			mem->dirty_param.dirty_background_bytes;
+	default:
+		BUG();
+	}
+}
+
+static int
+mem_cgroup_dirty_write_string(struct cgroup *cgrp, struct cftype *cft,
+				const char *buffer)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+	int type = cft->private;
+	int ret = -EINVAL;
+	unsigned long long val;
+
+	if (!mem_cgroup_has_dirty_limit(memcg))
+		return ret;
+
+	switch (type) {
+	case MEM_CGROUP_DIRTY_LIMIT_IN_BYTES:
+		/* This function does all necessary parse...reuse it */
+		ret = res_counter_memparse_write_strategy(buffer, &val);
+		if (ret)
+			break;
+		memcg->dirty_param.dirty_bytes = val;
+		memcg->dirty_param.dirty_ratio  = 0;
+		break;
+	case MEM_CGROUP_DIRTY_BACKGROUND_LIMIT_IN_BYTES:
+		ret = res_counter_memparse_write_strategy(buffer, &val);
+		if (ret)
+			break;
+		memcg->dirty_param.dirty_background_bytes = val;
+		memcg->dirty_param.dirty_background_ratio = 0;
+		break;
+	default:
+		BUG();
+		break;
+	}
+	return ret;
+}
+
+static int
+mem_cgroup_dirty_write(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+	int type = cft->private;
+
+	if (!mem_cgroup_has_dirty_limit(memcg))
+		return -EINVAL;
+	if ((type == MEM_CGROUP_DIRTY_RATIO ||
+	     type == MEM_CGROUP_DIRTY_BACKGROUND_RATIO) && val > 100)
+		return -EINVAL;
+	switch (type) {
+	case MEM_CGROUP_DIRTY_RATIO:
+		memcg->dirty_param.dirty_ratio = val;
+		memcg->dirty_param.dirty_bytes = 0;
+		break;
+	case MEM_CGROUP_DIRTY_BACKGROUND_RATIO:
+		memcg->dirty_param.dirty_background_ratio = val;
+		memcg->dirty_param.dirty_background_bytes = 0;
+		break;
+	default:
+		BUG();
+		break;
+	}
+	return 0;
+}
+
 static struct cftype mem_cgroup_files[] = {
 	{
 		.name = "usage_in_bytes",
@@ -4701,6 +4791,30 @@ static struct cftype mem_cgroup_files[] = {
 		.unregister_event = mem_cgroup_oom_unregister_event,
 		.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
 	},
+	{
+		.name = "dirty_ratio",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_u64 = mem_cgroup_dirty_write,
+		.private = MEM_CGROUP_DIRTY_RATIO,
+	},
+	{
+		.name = "dirty_limit_in_bytes",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_string = mem_cgroup_dirty_write_string,
+		.private = MEM_CGROUP_DIRTY_LIMIT_IN_BYTES,
+	},
+	{
+		.name = "dirty_background_ratio",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_u64 = mem_cgroup_dirty_write,
+		.private = MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
+	},
+	{
+		.name = "dirty_background_limit_in_bytes",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_string = mem_cgroup_dirty_write_string,
+		.private = MEM_CGROUP_DIRTY_BACKGROUND_LIMIT_IN_BYTES,
+	},
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
-- 
1.7.3.1

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