kill -3 java_pid命令將輸出java進(jìn)程的線程信息。
在AIX上在域的目錄下生成javacore文件
在linux上，信息將輸出到console
對(duì)于thread dump信息，主要關(guān)注的是線程的狀態(tài)和其執(zhí)行堆棧
線程的狀態(tài)一般為三類
Runnable（R）：當(dāng)前可以運(yùn)行的線程
Waiting on monitor（CW）：線程主動(dòng)wait
Waiting for monitor entry（MW）：線程等鎖
一般關(guān)注的都是第一和第三種狀態(tài)的線程
Cpu很忙則關(guān)注runnable的線程
Cpu閑則關(guān)注waiting for monitor entry的線程
狀態(tài)參考：
R － Running or runnable thread
S － Suspended thread
CW－ Thread waiting on a condition variable（it is in a Thread.sleep or in a synchronized wait.）
MW － Thread waiting on a monitor lock（等待一個(gè)線程鎖）
MS － Thread suspended waiting on a monitor lock（there is a good chance it is a bug. ）
Monitors are used to manage access to code that should only be run by a single thread at a time. A monitor can be thought of as a lock on an object, and every object has a monitor. （Monitor其實(shí)就是對(duì)象上面的鎖，提供多線程使用一個(gè)對(duì)象的機(jī)制）
Monitor類型：
utf8 hash table －Locks the hashtable of defined i18N Strings that were loaded from the class constant pool.
JNI pinning lock－ Protects block copies of arrays to native method code.
JNI global reference lock －Locks the global reference table which holds values that need to be explicitly freed, and will outlive the lifetime of the native method call.
BinClass lock－ Locks access to the loaded and resolved classes list. The global table list of classes
Class linking lock－ Protects a classes data when loading native libraries to resolve symbolic references
System class loader lock－ Ensures that only one thread is loading a system class at a time.
Code rewrite lock －Protects code when an optimization is attempted.
Heap lock－ Protects the Java heap during heap memory management
Monitor cache lock －Only one thread can have access to the monitor cache at a time this lock ensures the integrity of the monitor cache
Dynamic loading lock－ Protects Unix green threads JVMs from loading the shared library stub libdl.so more than once at a time.
Monitor IO lock －Protects physical I/O for example, open and read.
User signal monitor－ Controls access to the signal handler if a user signal USRSIG in green threads JVMs.
Child death monitor －Controls access to the process wait information when using the runtime system calls to run locals commands in a green threads JVM.
I/O Monitor －Controls access to the threads file descriptors for poll/select events
Alarm Monitor－ Controls access to a clock handler used in green threads JVMs to handle timeouts
Thread queue lock －Protects the queue of active threads
Monitor registry －Only one thread can have access to the monitor registry at a time this lock ensures the integrity of that registry
Has finalization queue lock *－ Protects the list of queue lock objects that have been garbage-collected, and deemed to need finalization. They are copied to the Finalize me queue
Finalize me queue lock * －Protects a list of objects that can be finalized at leisure
Name and type hash table lock * －Protects the JVM hash tables of constants and their types
String intern lock * －Locks the hashtable of defined Strings that were loaded from the class constant pool
Class loading lock * －Ensures only one thread loads a class at a time
Java stack lock * －Protects the free stack segments list
linux上查看線程
用于 Linux 的 JVM 將 Java 線程作為本地線程實(shí)現(xiàn)，這使每個(gè)線程成為一個(gè)獨(dú)立的 Linux 進(jìn)程。
使用top找出消耗cpu最多的進(jìn)程ID，把它轉(zhuǎn)換為16進(jìn)制數(shù)據(jù)，再threaddump文件中找nid＝0X2234E的線程，看它再做什么事情。
AIX上查看java進(jìn)程下所有線程的信息：
輸出線程ID
ps -mp 241888 -o THREAD
USER PID PPID TID ST CP PRI SC WCHAN F TT BND COMMAND
weblogic 241888 372868 - A 0 68 76 * 242001 - - /usr/java14/bin/java -Xms1024m -Xmx1024m -Dweblogic.Na
- - - 663693 Z 0 68 1 - c00001 - - -
- - - 671855 S 0 68 1 f100070f1000a440 8410400 - - -
- - - 753805 S 0 68 1 f100070f1000b840 8410400 - - -
- - - 766023 S 0 68 1 f10001001fe6aeb0 410400 - - -
- - - 774329 S 0 68 1 f100070f1000bd40 8410400 - - -
- - - 790667 S 0 68 1 f100070f1000c140 8410400 - - -
- - - 794635 S 0 68 1 f100070f1000c240 8410400 - - -
- - - 798813 S 0 68 1 f100070f1000c340 8410400 - - -
- - - 803021 Z 0 68 1 - c00001 - - -
- - - 807051 S 0 68 1 f100070f1000c540 8410400 - - -
- - - 811149 S 0 68 1 f100070f1000c640 8410400 - - -
