add config item

config/config.go

@@ -373,6 +373,7 @@ type Status struct {
 type Performance struct {
 	MaxProcs              uint    `toml:"max-procs" json:"max-procs"`
 	MaxMemory             uint64  `toml:"max-memory" json:"max-memory"`
+	ServerMemoryQuota     uint64  `toml:"server-memory-quota" json:"server-memory-quota"`
 	MemoryUsageAlarmRatio float64 `toml:"memory-usage-alarm-ratio" json:"memory-usage-alarm-ratio"`
 	StatsLease            string  `toml:"stats-lease" json:"stats-lease"`
 	StmtCountLimit        uint    `toml:"stmt-count-limit" json:"stmt-count-limit"`
@@ -610,6 +611,7 @@ var defaultConf = Config{
 	},
 	Performance: Performance{
 		MaxMemory:             0,
+		ServerMemoryQuota:     0,
 		MemoryUsageAlarmRatio: 0.8,
 		TCPKeepAlive:          true,
 		CrossJoin:             true,

config/config.toml.example

@@ -210,6 +210,9 @@ max-procs = 0
 # Max memory size to use, 0 use the total usable memory in the machine.
 max-memory = 0
 
+# Memory size quota for tidb server, 0 means unlimited
+server-memory-quota = 0
+
 # The alarm threshold when memory usage of the tidb-server exceeds. The valid value range is greater than or equal to 0
 # and less than or equal to 1. The default value is 0.8.
 # If this configuration is set to 0 or 1, it'll disable the alarm.

util/expensivequery/memory_usage_alarm.go

@@ -51,7 +51,7 @@ func initMemoryUsageAlarmRecord() (record *memoryUsageAlarm) {
 		record.err = errors.New("close memory usage alarm recorder")
 		return
 	}
-	if quota := config.GetGlobalConfig().Performance.MaxMemory; quota != 0 {
+	if quota := config.GetGlobalConfig().Performance.ServerMemoryQuota; quota != 0 {
 		record.serverMemoryQuota = quota
 		record.isServerMemoryQuotaSet = true
 	} else {