[RFC PATCH 3/5] mgmcg VM overcommit interface

[Andrea Righi <righi.andrea@gmail.com>]

Per-cgroup overcommit_memory and overcommit_ratio parameters can be shown
and/or manipulated using the files "memory.overcommit_memory" and
"memory.overcommit_ratio" in the cgroup filesystem.

The file "overcommit_as" can be used to retrieve the current committed space
and limit of each cgroup.

Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
---
 mm/memcontrol.c |  116 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 115 insertions(+), 1 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4100e24..e3e34e9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -36,6 +36,8 @@
 
 #include <asm/uaccess.h>
 
+#define K(x) ((x) << (PAGE_SHIFT - 10))
+
 struct cgroup_subsys mem_cgroup_subsys;
 static const int MEM_CGROUP_RECLAIM_RETRIES = 5;
 static struct kmem_cache *page_cgroup_cache;
@@ -47,7 +49,7 @@ 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_CACHE,	   /* # of pages charged as cache */
 	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as rss */
 	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
 	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
@@ -55,6 +57,11 @@ enum mem_cgroup_stat_index {
 	MEM_CGROUP_STAT_NSTATS,
 };
 
+enum mem_cgroup_vmacct_index {
+	MEM_CGROUP_OVERCOMMIT_MEMORY,
+	MEM_CGROUP_OVERCOMMIT_RATIO,
+};
+
 struct mem_cgroup_stat_cpu {
 	s64 count[MEM_CGROUP_STAT_NSTATS];
 } ____cacheline_aligned_in_smp;
@@ -995,6 +1002,97 @@ static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
 				mem_cgroup_write_strategy);
 }
 
+static ssize_t mem_cgroup_committed_read(struct cgroup *cont,
+					 struct cftype *cft,
+					 struct file *file,
+					 char __user *userbuf,
+					 size_t nbytes,
+					 loff_t *ppos)
+{
+	struct mem_cgroup *mem;
+	char *page;
+	unsigned long total, committed, allowed;
+	ssize_t count;
+	int ret;
+
+	page = (char *)__get_free_page(GFP_TEMPORARY);
+	if (unlikely(!page))
+		return -ENOMEM;
+
+	cgroup_lock();
+	if (cgroup_is_removed(cont)) {
+		cgroup_unlock();
+		ret = -ENODEV;
+		goto out;
+	}
+
+	mem = mem_cgroup_from_cont(cont);
+	committed = atomic_long_read(&mem->vmacct.vm_committed_space);
+
+	total = (long)(mem->res.limit >> PAGE_SHIFT) + 1L;
+	if (total > (totalram_pages - hugetlb_total_pages()))
+		allowed = ((totalram_pages - hugetlb_total_pages())
+			* mem->vmacct.overcommit_ratio / 100)
+			+ total_swap_pages;
+	else
+		allowed = total * mem->vmacct.overcommit_ratio / 100
+			+ total_swap_pages;
+	cgroup_unlock();
+
+	count = sprintf(page, "CommitLimit:  %8lu kB\n"
+			      "Committed_AS: %8lu kB\n",
+			      K(allowed), K(committed));
+	ret = simple_read_from_buffer(userbuf, nbytes, ppos, page, count);
+out:
+	free_page((unsigned long)page);
+	return ret;
+}
+
+static s64 mem_cgroup_vmacct_read_s64(struct cgroup *cont, struct cftype *cft)
+{
+	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
+	enum mem_cgroup_vmacct_index type = cft->private;
+
+	switch (type) {
+	case MEM_CGROUP_OVERCOMMIT_MEMORY:
+		return mem->vmacct.overcommit_memory;
+	case MEM_CGROUP_OVERCOMMIT_RATIO:
+		return mem->vmacct.overcommit_ratio;
+	default:
+		BUG();
+	}
+}
+
+static int mem_cgroup_vmacct_write_s64(struct cgroup *cont, struct cftype *cft,
+				       s64 val)
+{
+	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
+	enum mem_cgroup_vmacct_index type = cft->private;
+	int ret = 0;
+
+	cgroup_lock();
+	if (cgroup_is_removed(cont)) {
+		cgroup_unlock();
+		return -ENODEV;
+	}
+
+	switch (type) {
+	case MEM_CGROUP_OVERCOMMIT_MEMORY:
+		mem->vmacct.overcommit_memory = (int)val;
+		break;
+	case MEM_CGROUP_OVERCOMMIT_RATIO:
+		mem->vmacct.overcommit_ratio = (int)val;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	cgroup_unlock();
+
+	return ret;
+
+}
+
 static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
 {
 	struct mem_cgroup *mem;
@@ -1086,6 +1184,22 @@ static struct cftype mem_cgroup_files[] = {
 		.name = "stat",
 		.read_map = mem_control_stat_show,
 	},
+	{
+		.name = "overcommit_memory",
+		.private = MEM_CGROUP_OVERCOMMIT_MEMORY,
+		.read_s64 = mem_cgroup_vmacct_read_s64,
+		.write_s64 = mem_cgroup_vmacct_write_s64,
+	},
+	{
+		.name = "overcommit_ratio",
+		.private = MEM_CGROUP_OVERCOMMIT_RATIO,
+		.read_s64 = mem_cgroup_vmacct_read_s64,
+		.write_s64 = mem_cgroup_vmacct_write_s64,
+	},
+	{
+		.name = "overcommit_as",
+		.read = mem_cgroup_committed_read,
+	},
 };
 
 static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
-- 
1.5.4.3