chore: make cpu usage more smooth (#3842)

core/load/adaptiveshedder.go

@@ -136,7 +136,7 @@ func (as *adaptiveShedder) addFlying(delta int64) {
 	// update avgFlying when the request is finished.
 	// this strategy makes avgFlying have a little bit lag against flying, and smoother.
 	// when the flying requests increase rapidly, avgFlying increase slower, accept more requests.
-	// when the flying requests drop rapidly, avgFlying drop slower, accept less requests.
+	// when the flying requests drop rapidly, avgFlying drop slower, accept fewer requests.
 	// it makes the service to serve as more requests as possible.
 	if delta < 0 {
 		as.avgFlyingLock.Lock()

core/stat/internal/cpu_linux.go

@@ -14,6 +14,8 @@ import (
 const (
 	cpuTicks  = 100
 	cpuFields = 8
+	cpuMax    = 1000
+	statDir   = "/proc/stat"
 )
 
 var (
@@ -81,7 +83,10 @@ func RefreshCpu() uint64 {
 	cpuDelta := total - preTotal
 	systemDelta := system - preSystem
 	if cpuDelta > 0 && systemDelta > 0 {
-		usage = uint64(float64(cpuDelta*cores*1e3) / (float64(systemDelta) * quota))
+		usage = uint64(float64(cpuDelta*cores*cpuMax) / (float64(systemDelta) * quota))
+		if usage > cpuMax {
+			usage = cpuMax
+		}
 	}
 	preSystem = system
 	preTotal = total
@@ -117,7 +122,7 @@ func cpuSets() ([]uint64, error) {
 }
 
 func systemCpuUsage() (uint64, error) {
-	lines, err := iox.ReadTextLines("/proc/stat", iox.WithoutBlank())
+	lines, err := iox.ReadTextLines(statDir, iox.WithoutBlank())
 	if err != nil {
 		return 0, err
 	}