variable: control max/min gogc for gogctuner (#47148)

close #47166

sessionctx/variable/sysvar.go

@@ -830,6 +830,40 @@ var defaultSysVars = []*SysVar{
 		gctuner.GlobalMemoryLimitTuner.UpdateMemoryLimit()
 		return nil
 	}},
+	{Scope: ScopeGlobal, Name: TiDBGOGCTunerMaxValue, Value: strconv.Itoa(DefTiDBGOGCMaxValue),
+		Type: TypeInt, MinValue: 10, SetGlobal: func(_ context.Context, s *SessionVars, val string) error {
+			maxValue := TidbOptInt64(val, DefTiDBGOGCMaxValue)
+			gctuner.SetMaxGCPercent(uint32(maxValue))
+			gctuner.GlobalMemoryLimitTuner.UpdateMemoryLimit()
+			return nil
+		},
+		GetGlobal: func(ctx context.Context, vars *SessionVars) (string, error) {
+			return strconv.FormatInt(int64(gctuner.MaxGCPercent()), 10), nil
+		},
+		Validation: func(s *SessionVars, normalizedValue string, origin string, scope ScopeFlag) (string, error) {
+			maxValue := TidbOptInt64(origin, DefTiDBGOGCMaxValue)
+			if maxValue <= int64(gctuner.MinGCPercent()) {
+				return "", errors.New("tidb_gogc_tuner_max_value should be more than tidb_gogc_tuner_min_value")
+			}
+			return origin, nil
+		}},
+	{Scope: ScopeGlobal, Name: TiDBGOGCTunerMinValue, Value: strconv.Itoa(DefTiDBGOGCMinValue),
+		Type: TypeInt, MinValue: 10, SetGlobal: func(_ context.Context, s *SessionVars, val string) error {
+			minValue := TidbOptInt64(val, DefTiDBGOGCMinValue)
+			gctuner.SetMinGCPercent(uint32(minValue))
+			gctuner.GlobalMemoryLimitTuner.UpdateMemoryLimit()
+			return nil
+		},
+		GetGlobal: func(ctx context.Context, vars *SessionVars) (string, error) {
+			return strconv.FormatInt(int64(gctuner.MinGCPercent()), 10), nil
+		},
+		Validation: func(s *SessionVars, normalizedValue string, origin string, scope ScopeFlag) (string, error) {
+			minValue := TidbOptInt64(origin, DefTiDBGOGCMinValue)
+			if minValue >= int64(gctuner.MaxGCPercent()) {
+				return "", errors.New("tidb_gogc_tuner_min_value should be less than tidb_gogc_tuner_max_value")
+			}
+			return origin, nil
+		}},
 	{Scope: ScopeGlobal, Name: TiDBEnableTelemetry, Value: BoolToOnOff(DefTiDBEnableTelemetry), Type: TypeBool},
 	{Scope: ScopeGlobal, Name: TiDBEnableHistoricalStats, Value: On, Type: TypeBool, Depended: true},
 	/* tikv gc metrics */

sessionctx/variable/sysvar_test.go

@@ -1172,6 +1172,17 @@ func TestTiDBServerMemoryLimitGCTrigger(t *testing.T) {
 	require.Error(t, err)
 	err = mock.SetGlobalSysVar(context.Background(), TiDBServerMemoryLimitGCTrigger, "51%")
 	require.NoError(t, err)
+
+	err = mock.SetGlobalSysVar(context.Background(), TiDBGOGCTunerMaxValue, "50")
+	require.Error(t, err)
+	err = mock.SetGlobalSysVar(context.Background(), TiDBGOGCTunerMinValue, "200")
+	require.NoError(t, err)
+	err = mock.SetGlobalSysVar(context.Background(), TiDBGOGCTunerMinValue, "1000")
+	require.Error(t, err)
+	err = mock.SetGlobalSysVar(context.Background(), TiDBGOGCTunerMinValue, "100")
+	require.NoError(t, err)
+	err = mock.SetGlobalSysVar(context.Background(), TiDBGOGCTunerMaxValue, "200")
+	require.NoError(t, err)
 }
 
 func TestSetAggPushDownGlobally(t *testing.T) {

sessionctx/variable/tidb_vars.go

@@ -993,6 +993,10 @@ const (
 	TiDBEnableGOGCTuner = "tidb_enable_gogc_tuner"
 	// TiDBGOGCTunerThreshold is to control the threshold of GOGC tuner.
 	TiDBGOGCTunerThreshold = "tidb_gogc_tuner_threshold"
+	// TiDBGOGCTunerMaxValue is the max value of GOGC that GOGC tuner can change to.
+	TiDBGOGCTunerMaxValue = "tidb_gogc_tuner_max_value"
+	// TiDBGOGCTunerMinValue is the min value of GOGC that GOGC tuner can change to.
+	TiDBGOGCTunerMinValue = "tidb_gogc_tuner_min_value"
 	// TiDBExternalTS is the ts to read through when the `TiDBEnableExternalTsRead` is on
 	TiDBExternalTS = "tidb_external_ts"
 	// TiDBTTLJobEnable is used to enable/disable scheduling ttl job
@@ -1349,6 +1353,8 @@ const (
 	DefTiDBEnableGOGCTuner                       = true
 	// DefTiDBGOGCTunerThreshold is to limit TiDBGOGCTunerThreshold.
 	DefTiDBGOGCTunerThreshold                 float64 = 0.6
+	DefTiDBGOGCMaxValue                               = 500
+	DefTiDBGOGCMinValue                               = 100
 	DefTiDBOptPrefixIndexSingleScan                   = true
 	DefTiDBExternalTS                                 = 0
 	DefTiDBEnableExternalTSRead                       = false

util/gctuner/tuner.go

@@ -28,8 +28,7 @@ var (
 	minGCPercent atomic.Uint32
 
 	// EnableGOGCTuner is to control whether enable the GOGC tuner.
-	EnableGOGCTuner atomic.Bool
-
+	EnableGOGCTuner  atomic.Bool
 	defaultGCPercent uint32 = 100
 )
 
@@ -43,11 +42,21 @@ func SetMaxGCPercent(percent uint32) {
 	maxGCPercent.Store(percent)
 }
 
+// MaxGCPercent get the max cost of memory.
+func MaxGCPercent() uint32 {
+	return maxGCPercent.Load()
+}
+
 // SetMinGCPercent sets the max cost of memory.
 func SetMinGCPercent(percent uint32) {
 	minGCPercent.Store(percent)
 }
 
+// MinGCPercent get the min cost of memory.
+func MinGCPercent() uint32 {
+	return minGCPercent.Load()
+}
+
 func init() {
 	if val, err := strconv.Atoi(os.Getenv("GOGC")); err == nil {
 		defaultGCPercent = uint32(val)