Add the memory swappiness tuning option to docker.

Memory swappiness option takes 0-100, and helps to tune swappiness
behavior per container.
For example, When a lower value of swappiness is chosen
the container will see minimum major faults. When no value is
specified for memory-swappiness in docker UI, it is inherited from
parent cgroup. (generally 60 unless it is changed).

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>

sysinfo/sysinfo.go

@@ -13,9 +13,10 @@ type SysInfo struct {
 }
 
 type cgroupMemInfo struct {
-	MemoryLimit    bool
-	SwapLimit      bool
-	OomKillDisable bool
+	MemoryLimit      bool
+	SwapLimit        bool
+	OomKillDisable   bool
+	MemorySwappiness bool
 }
 
 type cgroupCpuInfo struct {

sysinfo/sysinfo_linux.go

@@ -50,6 +50,10 @@ func checkCgroupMem(quiet bool) *cgroupMemInfo {
 	if !quiet && !info.OomKillDisable {
 		logrus.Warnf("Your kernel does not support oom control.")
 	}
+	info.MemorySwappiness = cgroupEnabled(mountPoint, "memory.swappiness")
+	if !quiet && !info.MemorySwappiness {
+		logrus.Warnf("Your kernel does not support memory swappiness.")
+	}
 
 	return info
 }