storage: promote experimental-memory-mlock flag.

Since the memory mlock feature has been added as an experimental feature since v3.5 we want
to promote it as a stable feature as memory-mlock in v3.6. In v3.7 we will retire the
experimental-memory-mlock flag.

Signed-off-by: Jiayin Mao <jiayin.mao@datadoghq.com>

server/config/config.go

@@ -184,12 +184,15 @@ type ServerConfig struct {
 
 	DowngradeCheckTime time.Duration
 
-	// ExperimentalMemoryMlock enables mlocking of etcd owned memory pages.
+	// MemoryMlock enables mlocking of etcd owned memory pages.
 	// The setting improves etcd tail latency in environments were:
 	//   - memory pressure might lead to swapping pages to disk
 	//   - disk latency might be unstable
 	// Currently all etcd memory gets mlocked, but in future the flag can
 	// be refined to mlock in-use area of bbolt only.
+	MemoryMlock bool `json:"memory-mlock"`
+	// ExperimentalMemoryMlock has the same effect as MemoryMlock
+	// TODO: delete in v3.7
 	ExperimentalMemoryMlock bool `json:"experimental-memory-mlock"`
 
 	// ExperimentalTxnModeWriteWithSharedBuffer enable write transaction to use

server/embed/config.go

@@ -471,12 +471,17 @@ type Config struct {
 
 	ExperimentalDowngradeCheckTime time.Duration `json:"experimental-downgrade-check-time"`
 
-	// ExperimentalMemoryMlock enables mlocking of etcd owned memory pages.
+	// MemoryMlock enables mlocking of etcd owned memory pages.
 	// The setting improves etcd tail latency in environments were:
 	//   - memory pressure might lead to swapping pages to disk
 	//   - disk latency might be unstable
 	// Currently all etcd memory gets mlocked, but in future the flag can
 	// be refined to mlock in-use area of bbolt only.
+	MemoryMlock bool `json:"memory-mlock"`
+
+	// ExperimentalMemoryMlock has the same effect as MemoryMlock in v3.6.
+	// Deprecated in v3.6 and will be decommissioned in v3.7.
+	// TODO: Delete in v3.7
 	ExperimentalMemoryMlock bool `json:"experimental-memory-mlock"`
 
 	// ExperimentalTxnModeWriteWithSharedBuffer enables write transaction to use a shared buffer in its readonly check operations.
@@ -582,7 +587,8 @@ func NewConfig() *Config {
 		BcryptCost:   uint(bcrypt.DefaultCost),
 		AuthTokenTTL: 300,
 
-		PreVote: true,
+		PreVote:     true,
+		MemoryMlock: false,
 
 		loggerMu:              new(sync.RWMutex),
 		logger:                nil,
@@ -802,6 +808,8 @@ func (cfg *Config) AddFlags(fs *flag.FlagSet) {
 	fs.DurationVar(&cfg.ExperimentalWarningApplyDuration, "experimental-warning-apply-duration", cfg.ExperimentalWarningApplyDuration, "Time duration after which a warning is generated if request takes more time.")
 	fs.DurationVar(&cfg.WarningUnaryRequestDuration, "warning-unary-request-duration", cfg.WarningUnaryRequestDuration, "Time duration after which a warning is generated if a unary request takes more time.")
 	fs.DurationVar(&cfg.ExperimentalWarningUnaryRequestDuration, "experimental-warning-unary-request-duration", cfg.ExperimentalWarningUnaryRequestDuration, "Time duration after which a warning is generated if a unary request takes more time. It's deprecated, and will be decommissioned in v3.7. Use --warning-unary-request-duration instead.")
+	fs.BoolVar(&cfg.MemoryMlock, "memory-mlock", cfg.MemoryMlock, "Enable to enforce etcd pages (in particular bbolt) to stay in RAM.")
+	// TODO: delete in v3.7
 	fs.BoolVar(&cfg.ExperimentalMemoryMlock, "experimental-memory-mlock", cfg.ExperimentalMemoryMlock, "Enable to enforce etcd pages (in particular bbolt) to stay in RAM.")
 	fs.BoolVar(&cfg.ExperimentalTxnModeWriteWithSharedBuffer, "experimental-txn-mode-write-with-shared-buffer", true, "Enable the write transaction to use a shared buffer in its readonly check operations.")
 	fs.BoolVar(&cfg.ExperimentalStopGRPCServiceOnDefrag, "experimental-stop-grpc-service-on-defrag", cfg.ExperimentalStopGRPCServiceOnDefrag, "Enable etcd gRPC service to stop serving client requests on defragmentation.")

server/embed/etcd.go

@@ -208,6 +208,7 @@ func StartEtcd(inCfg *Config) (e *Etcd, err error) {
 		CorruptCheckTime:                     cfg.CorruptCheckTime,
 		CompactHashCheckTime:                 cfg.CompactHashCheckTime,
 		PreVote:                              cfg.PreVote,
+		MemoryMlock:                          cfg.MemoryMlock,
 		Logger:                               cfg.logger,
 		ForceNewCluster:                      cfg.ForceNewCluster,
 		EnableGRPCGateway:                    cfg.EnableGRPCGateway,

server/etcdmain/help.go

@@ -107,6 +107,8 @@ Member:
     Write timeout set on each rafthttp connection
   --feature-gates ''
     A set of key=value pairs that describe server level feature gates for alpha/experimental features. Options are:` + "\n    " + strings.Join(features.NewDefaultServerFeatureGate("", nil).KnownFeatures(), "\n    ") + `
+  --memory-mlock 'false'
+    Enable to enforce etcd pages (in particular bbolt) to stay in RAM.
 
 Clustering:
   --initial-advertise-peer-urls 'http://localhost:2380'

server/storage/backend.go

@@ -50,7 +50,8 @@ 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
+	// TODO: remove the cfg.ExperimentalMemoryMlock part in v3.7
+	bcfg.Mlock = cfg.MemoryMlock || cfg.ExperimentalMemoryMlock
 	bcfg.Hooks = hooks
 	return backend.New(bcfg)
 }