We run CI on cloud and the slaves are terminated after one time use, and new slaves are also created on demand. When the slaves number reaches 200 and the throuhput is very slow, and the stacktrace shows over 100 locks parking for

java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)

• parking to wait for <0x00007fd6f216d708> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
  at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
  at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
  at hudson.model.Queue._withLock(Queue.java:1291)
  at hudson.model.Queue.withLock(Queue.java:1176)
  at jenkins.model.Nodes.removeNode(Nodes.java:193)
  at jenkins.model.Jenkins.removeNode(Jenkins.java:1751)
  at hudson.plugins.ec2.EC2OndemandSlave.terminate(EC2OndemandSlave.java:72)
  at hudson.plugins.ec2.EC2OndemandSlave$terminate.call(Unknown Source)