etcd-io · omerap12 · Jan 3, 2025
diff --git a/server/embed/config_test.go b/server/embed/config_test.go
@@ -100,6 +100,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 		experimentalInitialCorruptCheck          string
 		experimentalCompactHashCheckEnabled      string
 		experimentalTxnModeWriteWithSharedBuffer string
+		experimentalMemoryMlock                  string
 		expectErr                                bool
 		expectedFeatures                         map[featuregate.Feature]bool
 	}{
@@ -130,6 +131,12 @@ func TestConfigFileFeatureGates(t *testing.T) {
 			experimentalTxnModeWriteWithSharedBuffer: "false",
 			expectErr:                                true,
 		},
+		{
+			name:                    "cannot set both experimental flag and feature gate flag for MemoryMlock",
+			serverFeatureGatesJSON:  "MemoryMlock=true",
+			experimentalMemoryMlock: "false",
+			expectErr:               true,
+		},
 		{
 			name:                                "ok to set different experimental flag and feature gate flag",
 			serverFeatureGatesJSON:              "DistributedTracing=true",
@@ -138,6 +145,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.DistributedTracing:      true,
 				features.StopGRPCServiceOnDefrag: true,
 				features.InitialCorruptCheck:     false,
+				features.MemoryMlock:             false,
 			},
 		},
 		{
@@ -160,6 +168,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.DistributedTracing:           false,
 				features.InitialCorruptCheck:          false,
 				features.TxnModeWriteWithSharedBuffer: true,
+				features.MemoryMlock:                  false,
 			},
 		},
 		{
@@ -170,6 +179,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.DistributedTracing:           false,
 				features.InitialCorruptCheck:          false,
 				features.TxnModeWriteWithSharedBuffer: true,
+				features.MemoryMlock:                  false,
 			},
 		},
 		{
@@ -179,6 +189,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.StopGRPCServiceOnDefrag: false,
 				features.DistributedTracing:      false,
 				features.InitialCorruptCheck:     true,
+				features.MemoryMlock:             false,
 			},
 		},
 		{
@@ -188,6 +199,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.StopGRPCServiceOnDefrag: false,
 				features.DistributedTracing:      false,
 				features.InitialCorruptCheck:     false,
+				features.MemoryMlock:             false,
 			},
 		},
 		{
@@ -199,6 +211,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.InitialCorruptCheck:          false,
 				features.CompactHashCheck:             false,
 				features.TxnModeWriteWithSharedBuffer: true,
+				features.MemoryMlock:                  false,
 			},
 		},
 		{
@@ -210,6 +223,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.InitialCorruptCheck:          false,
 				features.CompactHashCheck:             false,
 				features.TxnModeWriteWithSharedBuffer: false,
+				features.MemoryMlock:                  false,
 			},
 		},
 		{
@@ -219,6 +233,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.StopGRPCServiceOnDefrag: true,
 				features.DistributedTracing:      false,
 				features.InitialCorruptCheck:     false,
+				features.MemoryMlock:             false,
 			},
 		},
 		{
@@ -228,6 +243,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.StopGRPCServiceOnDefrag: false,
 				features.DistributedTracing:      false,
 				features.InitialCorruptCheck:     true,
+				features.MemoryMlock:             false,
 			},
 		},
 		{
@@ -237,6 +253,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.StopGRPCServiceOnDefrag: false,
 				features.DistributedTracing:      false,
 				features.InitialCorruptCheck:     false,
+				features.MemoryMlock:             false,
 			},
 		},
 		{
@@ -247,6 +264,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.DistributedTracing:           false,
 				features.InitialCorruptCheck:          false,
 				features.TxnModeWriteWithSharedBuffer: true,
+				features.MemoryMlock:                  false,
 			},
 		},
 		{
@@ -257,6 +275,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.DistributedTracing:           false,
 				features.InitialCorruptCheck:          false,
 				features.TxnModeWriteWithSharedBuffer: false,
+				features.MemoryMlock:                  false,
 			},
 		},
 		{
@@ -292,6 +311,24 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				features.CompactHashCheck:        true,
 			},
 		},
+		{
+			name:                   "can set feature gate MemoryMlock to true from feature gate flag",
+			serverFeatureGatesJSON: "MemoryMlock=true",
+			expectedFeatures: map[featuregate.Feature]bool{
+				features.StopGRPCServiceOnDefrag: false,
+				features.DistributedTracing:      false,
+				features.MemoryMlock:             true,
+			},
+		},
+		{
+			name:                   "can set feature gate MemoryMlock to false from feature gate flag",
+			serverFeatureGatesJSON: "MemoryMlock=false",
+			expectedFeatures: map[featuregate.Feature]bool{
+				features.StopGRPCServiceOnDefrag: false,
+				features.DistributedTracing:      false,
+				features.MemoryMlock:             false,
+			},
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
@@ -300,6 +337,7 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				ExperimentalInitialCorruptCheck          *bool  `json:"experimental-initial-corrupt-check,omitempty"`
 				ExperimentalCompactHashCheckEnabled      *bool  `json:"experimental-compact-hash-check-enabled,omitempty"`
 				ExperimentalTxnModeWriteWithSharedBuffer *bool  `json:"experimental-txn-mode-write-with-shared-buffer,omitempty"`
+				ExperimentalMemoryMlock                  *bool  `json:"experimental-memory-mlock,omitempty"`
 				ServerFeatureGatesJSON                   string `json:"feature-gates"`
 			}{
 				ServerFeatureGatesJSON: tc.serverFeatureGatesJSON,
@@ -337,6 +375,14 @@ func TestConfigFileFeatureGates(t *testing.T) {
 				yc.ExperimentalCompactHashCheckEnabled = &experimentalCompactHashCheckEnabled
 			}
 
+			if tc.experimentalMemoryMlock != "" {
+				experimentalMemoryMlock, err := strconv.ParseBool(tc.experimentalMemoryMlock)
+				if err != nil {
+					t.Fatal(err)
+				}
+				yc.ExperimentalMemoryMlock = &experimentalMemoryMlock
+			}
+
 			b, err := yaml.Marshal(&yc)
 			if err != nil {
 				t.Fatal(err)

diff --git a/server/embed/etcd.go b/server/embed/etcd.go
@@ -220,7 +220,6 @@ func StartEtcd(inCfg *Config) (e *Etcd, err error) {
 		DowngradeCheckTime:                   cfg.ExperimentalDowngradeCheckTime,
 		WarningApplyDuration:                 cfg.ExperimentalWarningApplyDuration,
 		WarningUnaryRequestDuration:          cfg.WarningUnaryRequestDuration,
-		ExperimentalMemoryMlock:              cfg.ExperimentalMemoryMlock,
 		ExperimentalBootstrapDefragThresholdMegabytes: cfg.ExperimentalBootstrapDefragThresholdMegabytes,
 		ExperimentalMaxLearners:                       cfg.ExperimentalMaxLearners,
 		V2Deprecation:                                 cfg.V2DeprecationEffective(),

diff --git a/server/etcdmain/help.go b/server/etcdmain/help.go
@@ -309,7 +309,7 @@ Experimental feature:
     Duration of time between two downgrade status checks.
   --experimental-enable-lease-checkpoint-persist 'false'
     Enable persisting remainingTTL to prevent indefinite auto-renewal of long lived leases. Always enabled in v3.6. Should be used to ensure smooth upgrade from v3.5 clusters with this feature enabled. Requires experimental-enable-lease-checkpoint to be enabled.
-  --experimental-memory-mlock
+  --experimental-memory-mlock. It's deprecated, and will be decommissioned in v3.7. Use '--feature-gates=MemoryMlock=true' instead.
     Enable to enforce etcd pages (in particular bbolt) to stay in RAM.
   --experimental-snapshot-catchup-entries
     Number of entries for a slow follower to catch up after compacting the raft storage entries.

diff --git a/server/features/etcd_features.go b/server/features/etcd_features.go
@@ -60,6 +60,11 @@ const (
 	// alpha: v3.6
 	// main PR: https://github.com/etcd-io/etcd/pull/14120
 	CompactHashCheck featuregate.Feature = "CompactHashCheck"
+	// MemoryMlock enables mlock memory to prevent etcd from being swapped to disk.
+	// owner: @ptabor
+	// alpha: v3.6
+	// main PR: https://github.com/etcd-io/etcd/pull/12750
+	MemoryMlock featuregate.Feature = "MemoryMlock"
 )
 
 var (
@@ -69,6 +74,7 @@ var (
 		InitialCorruptCheck:          {Default: false, PreRelease: featuregate.Alpha},
 		CompactHashCheck:             {Default: false, PreRelease: featuregate.Alpha},
 		TxnModeWriteWithSharedBuffer: {Default: true, PreRelease: featuregate.Beta},
+		MemoryMlock:                  {Default: false, PreRelease: featuregate.Alpha},
 	}
 	// ExperimentalFlagToFeatureMap is the map from the cmd line flags of experimental features
 	// to their corresponding feature gates.
@@ -78,6 +84,7 @@ var (
 		"experimental-initial-corrupt-check":             InitialCorruptCheck,
 		"experimental-compact-hash-check-enabled":        CompactHashCheck,
 		"experimental-txn-mode-write-with-shared-buffer": TxnModeWriteWithSharedBuffer,
+		"experimental-memory-mlock":                      MemoryMlock,
 	}
 )
 

diff --git a/server/storage/backend.go b/server/storage/backend.go
@@ -23,6 +23,7 @@ import (
 
 	"go.etcd.io/etcd/server/v3/config"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/snap"
+	"go.etcd.io/etcd/server/v3/features"
 	"go.etcd.io/etcd/server/v3/storage/backend"
 	"go.etcd.io/etcd/server/v3/storage/schema"
 	"go.etcd.io/raft/v3/raftpb"
@@ -50,7 +51,7 @@ func newBackend(cfg config.ServerConfig, hooks backend.Hooks) backend.Backend {
 		// permit 10% excess over quota for disarm
 		bcfg.MmapSize = uint64(cfg.QuotaBackendBytes + cfg.QuotaBackendBytes/10)
 	}
-	bcfg.Mlock = cfg.ExperimentalMemoryMlock
+	bcfg.Mlock = cfg.ServerFeatureGate.Enabled(features.MemoryMlock)
 	bcfg.Hooks = hooks
 	return backend.New(bcfg)
 }