This is an automated cherry-pick of pingcap#48096

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

tidb-server/main.go

@@ -206,6 +206,7 @@ func main() {
 		checkTempStorageQuota()
 	}
 	setupLog()
+	memory.InitMemoryHook()
 	setupExtensions()
 	setupStmtSummary()
 

util/memory/meminfo.go

@@ -20,10 +20,17 @@ import (
 
 	"github.com/pingcap/failpoint"
 	"github.com/pingcap/sysutil"
+<<<<<<< HEAD:util/memory/meminfo.go
 	"github.com/pingcap/tidb/parser/terror"
 	"github.com/pingcap/tidb/util/cgroup"
 	"github.com/pingcap/tidb/util/mathutil"
+=======
+	"github.com/pingcap/tidb/pkg/parser/terror"
+	"github.com/pingcap/tidb/pkg/util/cgroup"
+	"github.com/pingcap/tidb/pkg/util/logutil"
+>>>>>>> 4667ed9e168 (*: support cgroup with systemd (#48096)):pkg/util/memory/meminfo.go
 	"github.com/shirou/gopsutil/v3/mem"
+	"go.uber.org/zap"
 )
 
 // MemTotal returns the total amount of RAM on this system
@@ -51,6 +58,10 @@ func MemTotalNormal() (uint64, error) {
 	if time.Since(t) < 60*time.Second {
 		return total, nil
 	}
+	return memTotalNormal()
+}
+
+func memTotalNormal() (uint64, error) {
 	v, err := mem.VirtualMemory()
 	if err != nil {
 		return v.Total, err
@@ -140,6 +151,7 @@ func MemUsedCGroup() (uint64, error) {
 	return memo, nil
 }
 
+// it is for test and init.
 func init() {
 	if cgroup.InContainer() {
 		MemTotal = MemTotalCGroup
@@ -164,6 +176,37 @@ func init() {
 	terror.MustNil(err)
 }
 
+// InitMemoryHook initializes the memory hook.
+// It is to solve the problem that tidb cannot read cgroup in the systemd.
+// so if we are not in the container, we compare the cgroup memory limit and the physical memory,
+// the cgroup memory limit is smaller, we use the cgroup memory hook.
+func InitMemoryHook() {
+	if cgroup.InContainer() {
+		logutil.BgLogger().Info("use cgroup memory hook because TiDB is in the container")
+		return
+	}
+	cgroupValue, err := cgroup.GetMemoryLimit()
+	if err != nil {
+		return
+	}
+	physicalValue, err := memTotalNormal()
+	if err != nil {
+		return
+	}
+	if physicalValue > cgroupValue && cgroupValue != 0 {
+		MemTotal = MemTotalCGroup
+		MemUsed = MemUsedCGroup
+		sysutil.RegisterGetMemoryCapacity(MemTotalCGroup)
+		logutil.BgLogger().Info("use cgroup memory hook", zap.Int64("cgroupMemorySize", int64(cgroupValue)), zap.Int64("physicalMemorySize", int64(physicalValue)))
+	} else {
+		logutil.BgLogger().Info("use physical memory hook", zap.Int64("cgroupMemorySize", int64(cgroupValue)), zap.Int64("physicalMemorySize", int64(physicalValue)))
+	}
+	_, err = MemTotal()
+	terror.MustNil(err)
+	_, err = MemUsed()
+	terror.MustNil(err)
+}
+
 // InstanceMemUsed returns the memory usage of this TiDB server
 func InstanceMemUsed() (uint64, error) {
 	used, t := serverMemUsage.get()