config: add GOGC under performance section (pingcap#20872)

config/config.go

@@ -387,6 +387,7 @@ type Performance struct {
 	DistinctAggPushDown  bool    `toml:"distinct-agg-push-down" json:"agg-push-down-join"`
 	CommitterConcurrency int     `toml:"committer-concurrency" json:"committer-concurrency"`
 	MaxTxnTTL            uint64  `toml:"max-txn-ttl" json:"max-txn-ttl"`
+	GOGC                 int     `toml:"gogc" json:"gogc"`
 }
 
 // PlanCache is the PlanCache section of the config.
@@ -623,6 +624,7 @@ var defaultConf = Config{
 		DistinctAggPushDown:  false,
 		CommitterConcurrency: 16,
 		MaxTxnTTL:            10 * 60 * 1000, // 10min
+		GOGC:                 100,
 	},
 	ProxyProtocol: ProxyProtocol{
 		Networks:      "",

config/config.toml.example

@@ -258,6 +258,11 @@ committer-concurrency = 16
 # max lifetime of transaction ttl manager.
 max-txn-ttl = 600000
 
+# The Go GC trigger factor, you can get more information about it at https://golang.org/pkg/runtime.
+# If you encounter OOM when executing large query, you can decrease this value to trigger GC earlier.
+# If you find the CPU used by GC is too high or GC is too frequent and impact your business you can increase this value.
+gogc = 100
+
 [proxy-protocol]
 # PROXY protocol acceptable client networks.
 # Empty string means disable PROXY protocol, * means all networks.

tidb-server/main.go

@@ -512,6 +512,8 @@ func setGlobalVars() {
 	runtime.GOMAXPROCS(int(cfg.Performance.MaxProcs))
 	metrics.MaxProcs.Set(float64(runtime.GOMAXPROCS(0)))
 
+	util.SetGOGC(cfg.Performance.GOGC)
+
 	ddlLeaseDuration := parseDuration(cfg.Lease)
 	session.SetSchemaLease(ddlLeaseDuration)
 	statsLeaseDuration := parseDuration(cfg.Performance.StatsLease)

util/gogc.go

@@ -34,6 +34,9 @@ func init() {
 
 // SetGOGC update GOGC and related metrics.
 func SetGOGC(val int) {
+	if val <= 0 {
+		val = 100
+	}
 	debug.SetGCPercent(val)
 	metrics.GOGC.Set(float64(val))
 	atomic.StoreInt64(&gogcValue, int64(val))