diff --git a/src/configuration.go b/src/configuration.go
index 0fe430e..4c35b5d 100644
--- a/src/configuration.go
+++ b/src/configuration.go
@@ -21,6 +21,7 @@ type Configuration struct {
 	PreScheduleExtraTime   int      `json:"PreScheduleExtraTime"` /* seconds of schedule ahead except pre+post */
 	PreScheduleTimeout     int      `json:"PreScheduleTimeout"`
 	JobMaxRetries          int      `json:"scheduler.job_max_retries"`
+	PreemptEnabled         bool     `json:"scheduler.preempt_enabled"`
 
 	mock bool
 	mu   sync.Mutex
@@ -53,6 +54,7 @@ func InstanceOfConfiguration() *Configuration {
 			EnablePreScheduleRatio: 1.5,
 			PreScheduleExtraTime:   15,
 			JobMaxRetries:          0,
+			PreemptEnabled:         false,
 		}
 	}
 	return configurationInstance
@@ -124,6 +126,8 @@ func (config *Configuration) InitFromEnv() {
 			configurationInstance.JobMaxRetries = val
 		}
 	}
+	value = os.Getenv("scheduler.preempt_enabled")
+	configurationInstance.PreemptEnabled = value == "true"
 }
 
 func (config *Configuration) SetMockEnabled(enabled bool) bool {
@@ -166,6 +170,14 @@ func (config *Configuration) SetJobMaxRetries(value int) bool {
 	return true
 }
 
+func (config *Configuration) SetPreemptEnabled(enabled bool) bool {
+	config.mu.Lock()
+	defer config.mu.Unlock()
+	config.PreemptEnabled = enabled
+	log.Info("scheduler.preempt_enabled is set to ", enabled)
+	return true
+}
+
 func (config *Configuration) Dump() map[string]interface{} {
 	config.mu.Lock()
 	defer config.mu.Unlock()
@@ -183,6 +195,7 @@ func (config *Configuration) Dump() map[string]interface{} {
 	res["EnablePreScheduleRatio"] = config.EnablePreScheduleRatio
 	res["PreScheduleExtraTime"] = config.PreScheduleExtraTime
 	res["PreScheduleTimeout"] = config.PreScheduleTimeout
+	res["scheduler.preempt_enabled"] = config.PreemptEnabled
 	res["logger.level"] = log.LoggerLevel
 	res["logger.modules_disabled"] = log.LoggerModuleDisabled
 	return res
diff --git a/src/evaluator.go b/src/evaluator.go
index 0524335..32aab55 100644
--- a/src/evaluator.go
+++ b/src/evaluator.go
@@ -55,10 +55,11 @@ func (eva *Evaluator) add(node NodeStatus, task Task) {
 	if _, ok := eva.domains[task.Job][node.Domain]; !ok {
 		eva.domains[task.Job][node.Domain] = map[string]int{"PS": 0, "Worker": 0}
 	}
+	bwFactor := float64(task.BW)
 	if task.IsPS {
-		eva.costNetwork += eva.factorNode * float64(eva.racks[task.Job][node.Rack]["Worker"]-eva.nodes[task.Job][node.ClientID]["Worker"])
-		eva.costNetwork += eva.factorRack * float64(eva.domains[task.Job][node.Domain]["Worker"]-eva.racks[task.Job][node.Rack]["Worker"])
-		eva.costNetwork += eva.factorDomain * float64(eva.totalWorkers[task.Job]-eva.domains[task.Job][node.Domain]["Worker"])
+		eva.costNetwork += bwFactor * eva.factorNode * float64(eva.racks[task.Job][node.Rack]["Worker"]-eva.nodes[task.Job][node.ClientID]["Worker"])
+		eva.costNetwork += bwFactor * eva.factorRack * float64(eva.domains[task.Job][node.Domain]["Worker"]-eva.racks[task.Job][node.Rack]["Worker"])
+		eva.costNetwork += bwFactor * eva.factorDomain * float64(eva.totalWorkers[task.Job]-eva.domains[task.Job][node.Domain]["Worker"])
 
 		eva.nodes[task.Job][node.ClientID]["PS"]++
 		eva.racks[task.Job][node.Rack]["PS"]++
@@ -66,9 +67,9 @@ func (eva *Evaluator) add(node NodeStatus, task Task) {
 		eva.totalPSs[task.Job]++
 		eva.totalPS++
 	} else {
-		eva.costNetwork += eva.factorNode * float64(eva.racks[task.Job][node.Rack]["PS"]-eva.nodes[task.Job][node.ClientID]["PS"])
-		eva.costNetwork += eva.factorRack * float64(eva.domains[task.Job][node.Domain]["PS"]-eva.racks[task.Job][node.Rack]["PS"])
-		eva.costNetwork += eva.factorDomain * float64(eva.totalPSs[task.Job]-eva.domains[task.Job][node.Domain]["PS"])
+		eva.costNetwork += bwFactor * eva.factorNode * float64(eva.racks[task.Job][node.Rack]["PS"]-eva.nodes[task.Job][node.ClientID]["PS"])
+		eva.costNetwork += bwFactor * eva.factorRack * float64(eva.domains[task.Job][node.Domain]["PS"]-eva.racks[task.Job][node.Rack]["PS"])
+		eva.costNetwork += bwFactor * eva.factorDomain * float64(eva.totalPSs[task.Job]-eva.domains[task.Job][node.Domain]["PS"])
 
 		eva.nodes[task.Job][node.ClientID]["Worker"]++
 		eva.racks[task.Job][node.Rack]["Worker"]++
@@ -89,11 +90,12 @@ func (eva *Evaluator) add(node NodeStatus, task Task) {
 }
 
 func (eva *Evaluator) remove(node NodeStatus, task Task) {
+	bwFactor := float64(task.BW)
 	/* update network cost */
 	if task.IsPS {
-		eva.costNetwork -= eva.factorNode * float64(eva.racks[task.Job][node.Rack]["Worker"]-eva.nodes[task.Job][node.ClientID]["Worker"])
-		eva.costNetwork -= eva.factorRack * float64(eva.domains[task.Job][node.Domain]["Worker"]-eva.racks[task.Job][node.Rack]["Worker"])
-		eva.costNetwork -= eva.factorDomain * float64(eva.totalWorkers[task.Job]-eva.domains[task.Job][node.Domain]["Worker"])
+		eva.costNetwork -= bwFactor * eva.factorNode * float64(eva.racks[task.Job][node.Rack]["Worker"]-eva.nodes[task.Job][node.ClientID]["Worker"])
+		eva.costNetwork -= bwFactor * eva.factorRack * float64(eva.domains[task.Job][node.Domain]["Worker"]-eva.racks[task.Job][node.Rack]["Worker"])
+		eva.costNetwork -= bwFactor * eva.factorDomain * float64(eva.totalWorkers[task.Job]-eva.domains[task.Job][node.Domain]["Worker"])
 
 		eva.nodes[task.Job][node.ClientID]["PS"]--
 		eva.racks[task.Job][node.Rack]["PS"]--
@@ -101,9 +103,9 @@ func (eva *Evaluator) remove(node NodeStatus, task Task) {
 		eva.totalPSs[task.Job]--
 		eva.totalPS--
 	} else {
-		eva.costNetwork -= eva.factorNode * float64(eva.racks[task.Job][node.Rack]["PS"]-eva.nodes[task.Job][node.ClientID]["PS"])
-		eva.costNetwork -= eva.factorRack * float64(eva.domains[task.Job][node.Domain]["PS"]-eva.racks[task.Job][node.Rack]["PS"])
-		eva.costNetwork -= eva.factorDomain * float64(eva.totalPSs[task.Job]-eva.domains[task.Job][node.Domain]["PS"])
+		eva.costNetwork -= bwFactor * eva.factorNode * float64(eva.racks[task.Job][node.Rack]["PS"]-eva.nodes[task.Job][node.ClientID]["PS"])
+		eva.costNetwork -= bwFactor * eva.factorRack * float64(eva.domains[task.Job][node.Domain]["PS"]-eva.racks[task.Job][node.Rack]["PS"])
+		eva.costNetwork -= bwFactor * eva.factorDomain * float64(eva.totalPSs[task.Job]-eva.domains[task.Job][node.Domain]["PS"])
 
 		eva.nodes[task.Job][node.ClientID]["Worker"]--
 		eva.racks[task.Job][node.Rack]["Worker"]--
diff --git a/src/job_manager.go b/src/job_manager.go
index 6bcbde1..f134849 100644
--- a/src/job_manager.go
+++ b/src/job_manager.go
@@ -181,7 +181,7 @@ func (jm *JobManager) start() {
 		jm.statusMu.Lock()
 		for task, pre := range jm.lastHeartBeat {
 			if now-pre > 30 {
-				log.Warn(jm.job.Name, "-", task, " heartbeat longer tha 30s")
+				log.Warn(jm.job.Name, "-", task, " heartbeat longer than 30s")
 			}
 		}
 		jm.statusMu.Unlock()
diff --git a/src/logger.go b/src/logger.go
index 8d50f19..9971a9a 100644
--- a/src/logger.go
+++ b/src/logger.go
@@ -25,7 +25,7 @@ func (logger *Logger) Debug(args ...interface{}) {
 	if ok && details != nil {
 		module = details.Name()
 	}
-	args = append(args, "<--"+module)
+	args = append(args, " <-- "+module)
 	_log.Debug(args...)
 }
 
@@ -36,7 +36,7 @@ func (logger *Logger) Info(args ...interface{}) {
 	if ok && details != nil {
 		module = details.Name()
 	}
-	args = append(args, "<--"+module)
+	args = append(args, " <-- "+module)
 	_log.Info(args...)
 }
 
@@ -47,7 +47,7 @@ func (logger *Logger) Warn(args ...interface{}) {
 	if ok && details != nil {
 		module = details.Name()
 	}
-	args = append(args, "<--"+module)
+	args = append(args, " <-- "+module)
 	_log.Warn(args...)
 }
 
@@ -58,7 +58,7 @@ func (logger *Logger) Fatal(args ...interface{}) {
 	if ok && details != nil {
 		module = details.Name()
 	}
-	args = append(args, "<--"+module)
+	args = append(args, " <-- "+module)
 	_log.Fatal(args...)
 }
 
@@ -69,7 +69,7 @@ func (logger *Logger) Fatalf(format string, args ...interface{}) {
 	if ok && details != nil {
 		module = details.Name()
 	}
-	args = append(args, "<--"+module)
+	args = append(args, " <-- "+module)
 	_log.Fatalf(format, args...)
 }
 
diff --git a/src/main.go b/src/main.go
index c07c3b8..fdb35d4 100644
--- a/src/main.go
+++ b/src/main.go
@@ -96,9 +96,11 @@ func serverAPI(w http.ResponseWriter, r *http.Request) {
 			job.Name = job.Name + "-"
 			job.Name += strconv.FormatInt(time.Now().UnixNano(), 10)
 			job.Name += strconv.Itoa(10000 + rand.Intn(89999))
+			bwWorker := InstanceOfOptimizer().PredictReq(job, "Worker").BW
 			for i := range job.Tasks {
 				job.Tasks[i].ID = job.Name + ":" + job.Tasks[i].Name
 				job.Tasks[i].Job = job.Name
+				job.Tasks[i].BW = bwWorker
 			}
 			job.CreatedAt = int(time.Now().Unix())
 			msgSubmit.JobName = job.Name
@@ -336,6 +338,11 @@ func serverAPI(w http.ResponseWriter, r *http.Request) {
 			}
 			break
 
+			/* scheduler.preempt_enabled */
+		case "scheduler.preempt_enabled":
+			ok = InstanceOfConfiguration().SetPreemptEnabled(value == "true")
+			break
+
 			/* allocator.strategy */
 		case "allocator.strategy":
 			ok = InstanceOfAllocator().updateStrategy(value)
diff --git a/src/message.go b/src/message.go
index 03ec65d..14033cc 100644
--- a/src/message.go
+++ b/src/message.go
@@ -96,6 +96,7 @@ type MsgJobReq struct {
 	UtilGPU int    `json:"gpu_util"`
 	MemGPU  int    `json:"gpu_mem"`
 	BW      int    `json:"bw"`
+	Version int64  `json:"version"`
 }
 
 type MsgJobReqPredict struct {
diff --git a/src/optimizer.go b/src/optimizer.go
index 89d308d..3df533f 100644
--- a/src/optimizer.go
+++ b/src/optimizer.go
@@ -13,6 +13,7 @@ import (
 
 type Optimizer struct {
 	versions map[string]int
+	reqCache map[string]MsgJobReq
 	cache    map[string]OptimizerJobExecutionTime
 	cacheMu  sync.Mutex
 }
@@ -28,6 +29,7 @@ func InstanceOfOptimizer() *Optimizer {
 		optimizerInstance = &Optimizer{}
 		optimizerInstance.versions = map[string]int{}
 		optimizerInstance.cache = map[string]OptimizerJobExecutionTime{}
+		optimizerInstance.reqCache = map[string]MsgJobReq{}
 
 		go func() {
 			/* remove expired cache */
@@ -43,6 +45,15 @@ func InstanceOfOptimizer() *Optimizer {
 				for _, k := range expired {
 					delete(optimizerInstance.cache, k)
 				}
+				expired = []string{}
+				for k, v := range optimizerInstance.reqCache {
+					if time.Now().Unix()-v.Version > 300 {
+						expired = append(expired, k)
+					}
+				}
+				for _, k := range expired {
+					delete(optimizerInstance.reqCache, k)
+				}
 				optimizerInstance.cacheMu.Unlock()
 			}
 		}()
@@ -430,7 +441,13 @@ func (optimizer *Optimizer) trainReq(jobName string) {
 }
 
 func (optimizer *Optimizer) PredictReq(job Job, role string) MsgJobReq {
-	res := MsgJobReq{CPU: 4, Mem: 4096, UtilGPU: 100, MemGPU: 8192, BW: 0}
+	optimizer.cacheMu.Lock()
+	if val, ok := optimizer.reqCache[job.Name]; ok {
+		optimizer.cacheMu.Unlock()
+		return val
+	}
+	optimizer.cacheMu.Unlock()
+	res := MsgJobReq{CPU: 4, Mem: 4096, UtilGPU: 100, MemGPU: 8192, BW: 1}
 
 	var jobName string
 	str := strings.Split(job.Name, "-")
@@ -535,10 +552,14 @@ func (optimizer *Optimizer) PredictReq(job Job, role string) MsgJobReq {
 		if v, ok := tmp["gpu_mem"]; ok {
 			res.MemGPU = int(math.Ceil(v/1024)) * 1024
 		}
-		if v, ok := tmp["bw"]; ok {
-			res.BW = int(math.Ceil(v/10)) * 10
+		if v, ok := tmp["bw_rx"]; ok {
+			res.BW = int(math.Ceil(v / 100000))
 		}
 	}
+	res.Version = time.Now().Unix()
+	optimizer.cacheMu.Lock()
+	optimizer.reqCache[job.Name] = res
+	optimizer.cacheMu.Unlock()
 	return res
 }
 
diff --git a/src/scheduler_priority.go b/src/scheduler_priority.go
index a1bb5cf..763af34 100644
--- a/src/scheduler_priority.go
+++ b/src/scheduler_priority.go
@@ -17,7 +17,7 @@ type SchedulerPriority struct {
 	schedulingJobs map[string]bool
 	schedulingMu   sync.Mutex
 
-	jobMasters        map[string]*JobManager
+	jobMasters  map[string]*JobManager
 	enabled     bool
 	parallelism int
 }
@@ -68,7 +68,7 @@ func (scheduler *SchedulerPriority) Start() {
 					go func() {
 						jm.start()
 					}()
-				} else {
+				} else if InstanceOfConfiguration().PreemptEnabled {
 					/* start preempt */
 					var jobs []Job
 					preemptee := scheduler.queue[0]
diff --git a/src/util.go b/src/util.go
index 9792dcd..89c15d5 100644
--- a/src/util.go
+++ b/src/util.go
@@ -33,6 +33,7 @@ type Task struct {
 	Memory    int    `json:"memory"`
 	NumberGPU int    `json:"gpu_number"`
 	MemoryGPU int    `json:"gpu_memory"`
+	BW        int    `json:"bw"`
 	IsPS      bool   `json:"is_ps"`
 	ModelGPU  string `json:"gpu_model"`
 }