FATAL, Unable to delete script file, IOException2, remote file operation failed, unexpected termination of channel

Below is the stacktrace.

It happened when I ran two jobs on a master. After running a while, both jobs crashed with this exception.
I think this might be caused by a small flip-flop connectivity of the network, but I didn't noticed any disconnection.
Another cause may be the huge load of jenkins:

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
25942 hudson 15 0 6902m 5.8g 5720 S 0.3 74.3 401:22.30 java

Does the jenkins runs its own garbage collector at some specified time?
We have to restart every few days because it's getting slower and slower until hangs out.

FATAL: Unable to delete script file /tmp/hudson8303731085225956739.sh
hudson.util.IOException2: remote file operation failed: /tmp/hudson8303731085225956739.sh at hudson.remoting.Channel@30e472f4:build@autom-1
at hudson.FilePath.act(FilePath.java:781)
at hudson.FilePath.act(FilePath.java:767)
at hudson.FilePath.delete(FilePath.java:1022)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:92)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:58)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:695)
at hudson.model.Build$RunnerImpl.build(Build.java:178)
at hudson.model.Build$RunnerImpl.doRun(Build.java:139)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:461)
at hudson.model.Run.run(Run.java:1404)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:230)
Caused by: hudson.remoting.ChannelClosedException: channel is already closed
at hudson.remoting.Channel.send(Channel.java:499)
at hudson.remoting.Request.call(Request.java:110)
at hudson.remoting.Channel.call(Channel.java:681)
at hudson.FilePath.act(FilePath.java:774)
... 13 more
Caused by: java.io.IOException: Unexpected termination of the channel
at hudson.remoting.Channel$ReaderThread.run(Channel.java:1115)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2554)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at hudson.remoting.Channel$ReaderThread.run(Channel.java:1109)
FATAL: hudson.remoting.RequestAbortedException: java.io.IOException: Unexpected termination of the channel
hudson.remoting.RequestAbortedException: hudson.remoting.RequestAbortedException: java.io.IOException: Unexpected termination of the channel
at hudson.remoting.Request.call(Request.java:149)
at hudson.remoting.Channel.call(Channel.java:681)
at hudson.remoting.RemoteInvocationHandler.invoke(RemoteInvocationHandler.java:158)
at $Proxy29.join(Unknown Source)
at hudson.Launcher$RemoteLauncher$ProcImpl.join(Launcher.java:859)
at hudson.Launcher$ProcStarter.join(Launcher.java:345)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:82)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:58)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:695)
at hudson.model.Build$RunnerImpl.build(Build.java:178)
at hudson.model.Build$RunnerImpl.doRun(Build.java:139)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:461)
at hudson.model.Run.run(Run.java:1404)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:230)
Caused by: hudson.remoting.RequestAbortedException: java.io.IOException: Unexpected termination of the channel
at hudson.remoting.Request.abort(Request.java:273)
at hudson.remoting.Channel.terminate(Channel.java:732)
at hudson.remoting.Channel$ReaderThread.run(Channel.java:1139)
Caused by: java.io.IOException: Unexpected termination of the channel
at hudson.remoting.Channel$ReaderThread.run(Channel.java:1115)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2554)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at hudson.remoting.Channel$ReaderThread.run(Channel.java:1109)