Question

我复制了一个可疑的线程转储。我在调用java.net.SocketInputStream.socketRead0()时看到处于IN_NATIVE状态的173个线程在同一个呼叫中处于BLOCKED状态的30个线程我认为BLOCKED状态不消耗CPU，但它们正在等待IO。

IN_NATIVE状态下的线程怎么样？他们消耗CPU吗？任何想法，为什么我看到同一个调用socketRead0（）的不同线程状态？

173 threads
Thread 40283 - threadId:Thread 40283 - state:IN_NATIVE
stackTrace:
java.net.SocketInputStream.socketRead0(java.io.FileDescriptor, byte[], int, int, int) @bci=0 (Compiled frame; information may be imprecise)
java.net.SocketInputStream.read(byte[], int, int, int) @bci=87, line=152 (Compiled frame)
java.net.SocketInputStream.read(byte[], int, int) @bci=11, line=122 (Compiled frame)
com.sun.mail.util.TraceInputStream.read(byte[], int, int) @bci=7, line=110 (Compiled frame)
java.io.BufferedInputStream.fill() @bci=175, line=235 (Compiled frame)
java.io.BufferedInputStream.read() @bci=12, line=254 (Compiled frame)
com.sun.mail.util.LineInputStream.readLine() @bci=33, line=88 (Compiled frame)
com.sun.mail.smtp.SMTPTransport.readServerResponse() @bci=43, line=1589 (Compiled frame)
com.sun.mail.smtp.SMTPTransport.openServer(java.lang.String, int) @bci=117, line=1369 (Compiled frame)
com.sun.mail.smtp.SMTPTransport.protocolConnect(java.lang.String, int, java.lang.String, java.lang.String) @bci=270, line=412 (Compiled frame)
javax.mail.Service.connect(java.lang.String, int, java.lang.String, java.lang.String) @bci=380, line=288 (Compiled frame)
com.healthies.push.injectors.mailsenders.DefaultMailSender.sendMessage(com.healthies.push.messages.EmailMessage, javax.mail.internet.MimeMessage) @bci=28, line=63 (Compiled frame)
com.healthies.push.injectors.SMTPMessageInjector.sendMessage(com.healthies.push.injectors.mailsenders.MailSender, com.healthies.push.messages.EmailMessage, javax.mail.internet.MimeMessage) @bci=55, line=140 (Compiled frame)
com.healthies.push.injectors.SMTPMessageInjector.inject(com.healthies.push.messages.EmailMessage) @bci=210, line=117 (Compiled frame)
com.healthies.push.injectors.SMTPMessageInjector.inject(com.healthies.push.messages.Message) @bci=5, line=35 (Compiled frame)
com.healthies.push.injectors.EmailInjectorPool$1.run() @bci=85, line=40 (Compiled frame)
java.util.concurrent.Executors$RunnableAdapter.call() @bci=4, line=471 (Compiled frame)
java.util.concurrent.FutureTask.run() @bci=42, line=262 (Compiled frame)
java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=95, line=1145 (Compiled frame)
java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=615 (Interpreted frame)
java.lang.Thread.run() @bci=11, line=745 (Interpreted frame)
--------------------------------------------------------------------
30 threads 
Thread 40276 - threadId:Thread 40276 - state:BLOCKED
stackTrace:
java.net.SocketInputStream.socketRead0(java.io.FileDescriptor, byte[], int, int, int) @bci=0 (Compiled frame; information may be imprecise)
java.net.SocketInputStream.read(byte[], int, int, int) @bci=87, line=152 (Compiled frame)
java.net.SocketInputStream.read(byte[], int, int) @bci=11, line=122 (Compiled frame)
com.sun.mail.util.TraceInputStream.read(byte[], int, int) @bci=7, line=110 (Compiled frame)
java.io.BufferedInputStream.fill() @bci=175, line=235 (Compiled frame)
java.io.BufferedInputStream.read() @bci=12, line=254 (Compiled frame)
com.sun.mail.util.LineInputStream.readLine() @bci=33, line=88 (Compiled frame)
com.sun.mail.smtp.SMTPTransport.readServerResponse() @bci=43, line=1589 (Compiled frame)
com.sun.mail.smtp.SMTPTransport.issueSendCommand(java.lang.String, int) @bci=6, line=1494 (Compiled frame)
com.sun.mail.smtp.SMTPTransport.finishData() @bci=34, line=1321 (Compiled frame)
com.sun.mail.smtp.SMTPTransport.sendMessage(javax.mail.Message, javax.mail.Address[]) @bci=281, line=637 (Compiled frame)
com.healthies.push.injectors.mailsenders.DefaultMailSender.sendMessage(com.healthies.push.messages.EmailMessage, javax.mail.internet.MimeMessage) @bci=37, line=64 (Compiled frame)
com.healthies.push.injectors.SMTPMessageInjector.sendMessage(com.healthies.push.injectors.mailsenders.MailSender, com.healthies.push.messages.EmailMessage, javax.mail.internet.MimeMessage) @bci=55, line=140 (Compiled frame)
com.healthies.push.injectors.SMTPMessageInjector.inject(com.healthies.push.messages.EmailMessage) @bci=210, line=117 (Compiled frame)
com.healthies.push.injectors.SMTPMessageInjector.inject(com.healthies.push.messages.Message) @bci=5, line=35 (Compiled frame)
com.healthies.push.injectors.EmailInjectorPool$1.run() @bci=85, line=40 (Compiled frame)
java.util.concurrent.Executors$RunnableAdapter.call() @bci=4, line=471 (Compiled frame)
java.util.concurrent.FutureTask.run() @bci=42, line=262 (Compiled frame)
java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=95, line=1145 (Compiled frame)
java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=615 (Interpreted frame)
java.lang.Thread.run() @bci=11, line=745 (Interpreted frame)

Answer 1

通常，您永远不会看到线程在BLOCKED状态下执行非同步本机方法。但是这个转储是在强制模式（jstack -F）中获得的，works differently。

似乎JVM已请求safepoint operation。必须在安全点停止运行Java代码的所有线程，但仍可以运行本机方法。每当本机方法返回时，它都会检查安全点操作是否正在进行，如果是，则阻止当前线程，直到VM操作完成。

所以，在你的情况下

BLOCKED状态中的线程已经完成本机调用，并且正在等待方法返回时安全点操作的结束;
IN_NATIVE状态的线程仍在执行本机调用，可能在套接字读取时被阻止。

JVM无法将系统调用上阻止的本机方法与实际使用CPU的本机方法区分开来 - 在这两种情况下，它都会显示IN_NATIVE状态的线程。你不能从线程转储中得出这些线程是否繁忙的结论。

为了查看本机方法是否消耗CPU，您需要使用top，perf或native code aware profiler等实用程序。

Java线程转储CPU还是只是IO等待？

1 个答案: