cgroup: Collect some more stats from `memory.stat` file

This commit adds some more essential fields collected from `memory.stat`
file. There are two differences between Cgroup V1 and V2:
- `rss` in V1 is named `anon` in V2.
- `cache` in V1 is named `file` in V2.

The names in V2 reflect the meanings of underlying metrics better. Thus,
the reported stats use V2's names.

5 files changed, 48 insertions, 0 deletions

diff --git a/internal/cgroups/cgroups.go b/internal/cgroups/cgroups.go
index 9a8b96492..8cf8df116 100644
--- a/internal/cgroups/cgroups.go
+++ b/internal/cgroups/cgroups.go
@@ -34,6 +34,18 @@ type CgroupStats struct {
 	// UnderOOM is the current OOM status of a cgroup. This information is available for Cgroup V1 only. It's read
 	// from the `memory.oom_control` file.
 	UnderOOM bool
+	// Anon reflects the `rss` (V1) or `anon` (V2) of `memory.stat` file. That's amount of memory used in anonymous mappings
+	Anon uint64
+	// ActiveAnon reflects the `active_file` of `memory.stat` file, anonymous and swap cache memory on active LRU list.
+	ActiveAnon uint64
+	// InactiveAnon reflects the `inactive_anon` of `memory.stat` file, anonymous and swap cache memory on inactive LRU list.
+	InactiveAnon uint64
+	// File reflects the `cache` (V1) or `file` (V2) of `memory.stat` file, bytes of page cache memory.
+	File uint64
+	// ActiveFile reflects the `active_file` of `memory.stat` file, bytes of file-backed memory that cannot be reclaimed.
+	ActiveFile uint64
+	// InactiveFile reflects the `inactive_file` of `memory.stat` file, bytes of file-backed memory on inactive LRU list.
+	InactiveFile uint64
 }
 
 // Stats stores statistics of all cgroups managed by a manager
diff --git a/internal/cgroups/v1_linux.go b/internal/cgroups/v1_linux.go
index 92f2b6031..8783f2156 100644
--- a/internal/cgroups/v1_linux.go
+++ b/internal/cgroups/v1_linux.go
@@ -205,6 +205,12 @@ func (cvh *cgroupV1Handler) stats() (Stats, error) {
 			MemoryLimit:          metrics.Memory.Usage.Limit,
 			OOMKills:             metrics.MemoryOomControl.OomKill,
 			UnderOOM:             metrics.MemoryOomControl.UnderOom != 0,
+			Anon:                 metrics.Memory.RSS,
+			ActiveAnon:           metrics.Memory.ActiveAnon,
+			InactiveAnon:         metrics.Memory.InactiveAnon,
+			File:                 metrics.Memory.Cache,
+			ActiveFile:           metrics.Memory.ActiveFile,
+			InactiveFile:         metrics.Memory.InactiveFile,
 		},
 	}, nil
 }
diff --git a/internal/cgroups/v1_linux_test.go b/internal/cgroups/v1_linux_test.go
index cb28d40c0..dcb4358b8 100644
--- a/internal/cgroups/v1_linux_test.go
+++ b/internal/cgroups/v1_linux_test.go
@@ -574,6 +574,12 @@ oom_kill 3`},
 				{"cpu.stat", `nr_periods 10
 nr_throttled 50
 throttled_time 1000000`}, // 0.001 seconds
+				{"memory.stat", `cache 235000000
+rss 234000000
+inactive_anon 200000000
+active_anon 34000000
+inactive_file 100000000
+active_file 135000000`},
 			},
 			expectedStats: Stats{
 				ParentStats: CgroupStats{
@@ -583,6 +589,12 @@ throttled_time 1000000`}, // 0.001 seconds
 					MemoryLimit:          2000000000,
 					OOMKills:             3,
 					UnderOOM:             true,
+					Anon:                 234000000,
+					ActiveAnon:           34000000,
+					InactiveAnon:         200000000,
+					File:                 235000000,
+					ActiveFile:           135000000,
+					InactiveFile:         100000000,
 				},
 			},
 		},
diff --git a/internal/cgroups/v2_linux.go b/internal/cgroups/v2_linux.go
index 969c94e1f..cd2884de6 100644
--- a/internal/cgroups/v2_linux.go
+++ b/internal/cgroups/v2_linux.go
@@ -199,6 +199,12 @@ func (cvh *cgroupV2Handler) stats() (Stats, error) {
 			CPUThrottledDuration: float64(metrics.CPU.ThrottledUsec) / float64(time.Second),
 			MemoryUsage:          metrics.Memory.Usage,
 			MemoryLimit:          metrics.Memory.UsageLimit,
+			Anon:                 metrics.Memory.Anon,
+			ActiveAnon:           metrics.Memory.ActiveAnon,
+			InactiveAnon:         metrics.Memory.InactiveAnon,
+			File:                 metrics.Memory.File,
+			ActiveFile:           metrics.Memory.ActiveFile,
+			InactiveFile:         metrics.Memory.InactiveFile,
 		},
 	}
 	if metrics.MemoryEvents != nil {
diff --git a/internal/cgroups/v2_linux_test.go b/internal/cgroups/v2_linux_test.go
index 67b5bc2dc..a0042083d 100644
--- a/internal/cgroups/v2_linux_test.go
+++ b/internal/cgroups/v2_linux_test.go
@@ -546,6 +546,12 @@ oom_kill 5`},
 				{"cpu.stat", `nr_periods 10
 nr_throttled 50
 throttled_usec 1000000`}, // 0.001 seconds
+				{"memory.stat", `anon 234000000
+file 235000000
+inactive_anon 200000000
+active_anon 34000000
+inactive_file 100000000
+active_file 135000000`},
 			},
 			expectedStats: Stats{
 				ParentStats: CgroupStats{
@@ -554,6 +560,12 @@ throttled_usec 1000000`}, // 0.001 seconds
 					MemoryUsage:          1234000000,
 					MemoryLimit:          2000000000,
 					OOMKills:             5,
+					Anon:                 234000000,
+					ActiveAnon:           34000000,
+					InactiveAnon:         200000000,
+					File:                 235000000,
+					ActiveFile:           135000000,
+					InactiveFile:         100000000,
 				},
 			},
 		},