From 2d3c9cc70016cf9312114ab6310b3950165794eb Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Wed, 11 Nov 2020 13:19:33 +0800
Subject: [PATCH] config: add GOGC under performance section (#20872) (#20922)

---
 config/config.go           | 2 ++
 config/config.toml.example | 5 +++++
 tidb-server/main.go        | 2 ++
 util/gogc.go               | 3 +++
 4 files changed, 12 insertions(+)

diff --git a/config/config.go b/config/config.go
index 7b7c47319be30..a7e2c4fb85c63 100644
--- a/config/config.go
+++ b/config/config.go
@@ -389,6 +389,7 @@ 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.
@@ -627,6 +628,7 @@ var defaultConf = Config{
 		DistinctAggPushDown:   false,
 		CommitterConcurrency:  16,
 		MaxTxnTTL:             10 * 60 * 1000, // 10min
+		GOGC:                  100,
 	},
 	ProxyProtocol: ProxyProtocol{
 		Networks:      "",
diff --git a/config/config.toml.example b/config/config.toml.example
index 6556eee05ef1f..27de8e54831ca 100644
--- a/config/config.toml.example
+++ b/config/config.toml.example
@@ -269,6 +269,11 @@ 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.
diff --git a/tidb-server/main.go b/tidb-server/main.go
index f309173ff2c1d..2b5b5241ca495 100644
--- a/tidb-server/main.go
+++ b/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)
diff --git a/util/gogc.go b/util/gogc.go
index 3d49112825901..67d69a476848b 100644
--- a/util/gogc.go
+++ b/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))