[lxc-devel] [lxcfs/master] meminfo: align swap implementation with docs

brauner on Github lxc-bot at linuxcontainers.org
Thu Nov 5 19:22:01 UTC 2020


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From 77b37202eb163069ee202c73ad32f4f2d4a340af Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Thu, 5 Nov 2020 19:19:41 +0100
Subject: [PATCH 1/2] cgfsng: align method implementations

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 src/cgroups/cgfsng.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/src/cgroups/cgfsng.c b/src/cgroups/cgfsng.c
index 824b0e7..2d09f88 100644
--- a/src/cgroups/cgfsng.c
+++ b/src/cgroups/cgfsng.c
@@ -992,33 +992,33 @@ struct cgroup_ops *cgfsng_ops_init(void)
 	if (!cgfsng_ops)
 		return ret_set_errno(NULL, ENOMEM);
 
-	cgfsng_ops->cgroup_layout = CGROUP_LAYOUT_UNKNOWN;
-	cgfsng_ops->mntns_fd = -EBADF;
-	cgfsng_ops->cgroup2_root_fd = -EBADF;
+	cgfsng_ops->cgroup_layout		= CGROUP_LAYOUT_UNKNOWN;
+	cgfsng_ops->mntns_fd			= -EBADF;
+	cgfsng_ops->cgroup2_root_fd		= -EBADF;
 
 	if (cg_init(cgfsng_ops))
 		return NULL;
 
-	cgfsng_ops->num_hierarchies = cgfsng_num_hierarchies;
-	cgfsng_ops->get = cgfsng_get;
-	cgfsng_ops->get_hierarchies = cgfsng_get_hierarchies;
-	cgfsng_ops->get_hierarchy = cgfsng_get_hierarchy;
-	cgfsng_ops->driver = "cgfsng";
-	cgfsng_ops->version = "1.0.0";
-	cgfsng_ops->mount = cgfsng_mount;
+	cgfsng_ops->num_hierarchies		= cgfsng_num_hierarchies;
+	cgfsng_ops->get				= cgfsng_get;
+	cgfsng_ops->get_hierarchies		= cgfsng_get_hierarchies;
+	cgfsng_ops->get_hierarchy		= cgfsng_get_hierarchy;
+	cgfsng_ops->driver			= "cgfsng";
+	cgfsng_ops->version			= "1.0.0";
+	cgfsng_ops->mount			= cgfsng_mount;
 
 	/* memory */
-	cgfsng_ops->get_memory_stats_fd = cgfsng_get_memory_stats_fd;
-	cgfsng_ops->get_memory_stats = cgfsng_get_memory_stats;
-	cgfsng_ops->get_memory_max = cgfsng_get_memory_max;
-	cgfsng_ops->get_memory_swap_max = cgfsng_get_memory_swap_max;
-	cgfsng_ops->get_memory_current = cgfsng_get_memory_current;
-	cgfsng_ops->get_memory_swap_current = cgfsng_get_memory_swap_current;
-	cgfsng_ops->can_use_swap = cgfsng_can_use_swap;
+	cgfsng_ops->get_memory_stats_fd		= cgfsng_get_memory_stats_fd;
+	cgfsng_ops->get_memory_stats		= cgfsng_get_memory_stats;
+	cgfsng_ops->get_memory_max		= cgfsng_get_memory_max;
+	cgfsng_ops->get_memory_swap_max		= cgfsng_get_memory_swap_max;
+	cgfsng_ops->get_memory_current		= cgfsng_get_memory_current;
+	cgfsng_ops->get_memory_swap_current	= cgfsng_get_memory_swap_current;
+	cgfsng_ops->can_use_swap		= cgfsng_can_use_swap;
 
 	/* cpuset */
-	cgfsng_ops->get_cpuset_cpus = cgfsng_get_cpuset_cpus;
-	cgfsng_ops->can_use_cpuview = cgfsng_can_use_cpuview;
+	cgfsng_ops->get_cpuset_cpus		= cgfsng_get_cpuset_cpus;
+	cgfsng_ops->can_use_cpuview		= cgfsng_can_use_cpuview;
 
 	/* blkio */
 	cgfsng_ops->get_io_service_bytes	= cgfsng_get_io_service_bytes;

From 3b9c3c53ee34b908636b534f3eb2807d817f4765 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Thu, 5 Nov 2020 20:21:00 +0100
Subject: [PATCH 2/2] meminfo: align swap implementation with docs

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 src/cgroups/cgfsng.c |  7 +++++++
 src/cgroups/cgroup.h |  2 ++
 src/proc_fuse.c      | 45 ++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/src/cgroups/cgfsng.c b/src/cgroups/cgfsng.c
index 2d09f88..b369ed2 100644
--- a/src/cgroups/cgfsng.c
+++ b/src/cgroups/cgfsng.c
@@ -602,6 +602,12 @@ static int cgfsng_get_memory_stats_fd(struct cgroup_ops *ops, const char *cgroup
 	return openat(h->fd, path, O_RDONLY | O_CLOEXEC | O_NOFOLLOW);
 }
 
+static int cgfsng_get_memory_swappiness(struct cgroup_ops *ops,
+					const char *cgroup, char **value)
+{
+	return cgfsng_get_memory(ops, cgroup, "memory.swappiness", value);
+}
+
 static int cgfsng_get_memory_current(struct cgroup_ops *ops, const char *cgroup,
 				     char **value)
 {
@@ -1014,6 +1020,7 @@ struct cgroup_ops *cgfsng_ops_init(void)
 	cgfsng_ops->get_memory_swap_max		= cgfsng_get_memory_swap_max;
 	cgfsng_ops->get_memory_current		= cgfsng_get_memory_current;
 	cgfsng_ops->get_memory_swap_current	= cgfsng_get_memory_swap_current;
+	cgfsng_ops->get_memory_swappiness	= cgfsng_get_memory_swappiness;
 	cgfsng_ops->can_use_swap		= cgfsng_can_use_swap;
 
 	/* cpuset */
diff --git a/src/cgroups/cgroup.h b/src/cgroups/cgroup.h
index ad4a3ae..ba29b97 100644
--- a/src/cgroups/cgroup.h
+++ b/src/cgroups/cgroup.h
@@ -153,6 +153,8 @@ struct cgroup_ops {
 			      char **value);
 	int (*get_memory_swap_max)(struct cgroup_ops *ops, const char *cgroup,
 				   char **value);
+	int (*get_memory_swappiness)(struct cgroup_ops *ops, const char *cgroup,
+				     char **value);
 	bool (*can_use_swap)(struct cgroup_ops *ops);
 
 	/* cpuset */
diff --git a/src/proc_fuse.c b/src/proc_fuse.c
index 7bc1eb0..0d24b9e 100644
--- a/src/proc_fuse.c
+++ b/src/proc_fuse.c
@@ -310,6 +310,15 @@ static uint64_t get_min_memlimit(const char *cgroup, bool swap)
 	return retlimit;
 }
 
+static bool swappiness_is_off(const char *cgroup)
+{
+	__do_free char *swappiness_str = NULL;
+	int ret;
+
+	ret = cgroup_ops->get_memory_swappiness(cgroup_ops, cgroup, &swappiness_str);
+	return (ret > 0) && swappiness_str && (*swappiness_str == '0');
+}
+
 static inline bool startswith(const char *line, const char *pref)
 {
 	return strncmp(line, pref, strlen(pref)) == 0;
@@ -1141,7 +1150,8 @@ static int proc_meminfo_read(char *buf, size_t size, off_t offset,
 	__do_fclose FILE *f = NULL;
 	struct fuse_context *fc = fuse_get_context();
 	struct lxcfs_opts *opts = (struct lxcfs_opts *)fuse_get_context()->private_data;
-	bool wants_swap = opts && !opts->swap_off && liblxcfs_can_use_swap(), host_swap = false;
+	bool wants_swap = opts && !opts->swap_off && liblxcfs_can_use_swap(), host_swap = false,
+	     swappiness_off = false;
 	struct file_info *d = INTTYPE_TO_PTR(fi->fh);
 	uint64_t memlimit = 0, memusage = 0, memswlimit = 0, memswusage = 0,
 		 hosttotal = 0, swfree = 0, swusage = 0, swtotal = 0;
@@ -1195,6 +1205,7 @@ static int proc_meminfo_read(char *buf, size_t size, off_t offset,
 	 * turned off for current kernel.
 	 */
 	if (wants_swap) {
+		swappiness_off = swappiness_is_off(cgroup);
 		memswlimit = get_min_memlimit(cgroup, true);
 		if (memswlimit > 0) {
 			ret = cgroup_ops->get_memory_swap_current(cgroup_ops, cgroup, &memswusage_str);
@@ -1209,6 +1220,36 @@ static int proc_meminfo_read(char *buf, size_t size, off_t offset,
 					swusage = (memswusage - memusage) / 1024;
 			}
 		}
+
+		/*
+		 * If the swappiness is set to 0 and there is no SWAP usage, no
+		 * SWAP is reported. However if there is SWAP usage, then a
+		 * SWAP device of the size of the usage (100% full) is
+		 * reported. This provides adequate reporting of the memory
+		 * consumption while preventing applications from assuming more
+		 * SWAP is available.
+		 */
+		if (swappiness_off) {
+			if (swusage == 0) {
+				wants_swap = false;
+			} else {
+				swtotal = swusage;
+				swfree = 0;
+			}
+		}
+
+		/*
+		 * Because SWAP usage for a given container can exceed the
+		 * delta between RAM and RAM+SWAP, the SWAP size is always
+		 * reported to be the smaller of the RAM+SWAP limit or the host
+		 * SWAP device itself. This ensures that at no point SWAP usage
+		 * will be allowed to exceed the SWAP size.
+		 */
+		if (wants_swap && (swtotal > memlimit)) {
+			swtotal = memlimit;
+			swusage = memlimit;
+			swfree = 0;
+		}
 	}
 
 	f = fopen_cached("/proc/meminfo", "re", &fopen_cache);
@@ -1253,7 +1294,7 @@ static int proc_meminfo_read(char *buf, size_t size, off_t offset,
 				 * anyway.) so fallback to the host's values in
 				 * that case too.
 				 */
-				if ((hostswtotal < swtotal) || swtotal == 0) {
+				if ((hostswtotal < swtotal)) {
 					swtotal = hostswtotal;
 					host_swap = true;
 				}


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