[TOC] # 簡介 線上cpu 100%,定位問題辦法 4步 ~~~ 1.?top?oder?by?with?P：1040//?首先按進程負載排序找到??axLoad(pid) 2.?top -Hp 進程PID：1073//?找到相關負載?線程PID 3.?printf?“0x%x\\n”線程PID：?0x431//?將線程PID轉換為?16進制，為后面查找?jstack?日志做準備 4.?jstack??進程PID?|?vim?+/十六進制線程PID?-????????//?例如：jstack 1040|vim +/0x431?- ~~~ mac查看線程 ~~~ ps -M {pid} ~~~ 在ps命令中，“-T”選項可以開啟線程查看。下面的命令列出了由進程號為的進程創建的所有線程。 ~~~ ps -T -p {pid} ~~~ 將上面的流程封裝為了一個工具：`show-busy-java-threads.sh`（ https://github.com/oldratlee/useful-scripts ），可以很方便的定位線上的這類問題 快速安裝 ~~~ source <(curl -fsSL https://raw.githubusercontent.com/oldratlee/useful-scripts/master/test-cases/self-installer.sh) ~~~ # 案例 ## java 正則表達式回溯造成 CPU 100% ~~~ import java.util.ArrayList; import java.util.List; import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexLoad { public static void main(String[] args) { String[] patternMatch = {"([\\w\\s]+)+([+\\-/*])+([\\w\\s]+)", "([\\w\\s]+)+([+\\-/*])+([\\w\\s]+)+([+\\-/*])+([\\w\\s]+)"}; List<String> patternList = new ArrayList<String>(); patternList.add("Avg Volume Units product A + Volume Units product A"); patternList.add("Avg Volume Units / Volume Units product A"); patternList.add("Avg retailer On Hand / Volume Units Plan / Store Count"); patternList.add("Avg Hand Volume Units Plan Store Count"); patternList.add("1 - Avg merchant Volume Units"); patternList.add("Total retailer shipment Count"); for (String s :patternList ){ for(int i=0;i<patternMatch.length;i++){ Pattern pattern = Pattern.compile(patternMatch[i]); Matcher matcher = pattern.matcher(s); System.out.println(s); if (matcher.matches()) { System.out.println("Passed"); }else System.out.println("Failed;"); } } } } ~~~ 怎么使用呢？ ~~~ show-busy-java-threads.sh # 從 所有的 Java進程中找出最消耗CPU的線程（缺省5個），打印出其線程棧。 show-busy-java-threads.sh -c <要顯示的線程棧數> show-busy-java-threads.sh -c <要顯示的線程棧數> -p <指定的Java Process> # -F選項：執行jstack命令時加上-F選項（強制jstack），一般情況不需要使用 show-busy-java-threads.sh -p <指定的Java Process> -F show-busy-java-threads.sh -s <指定jstack命令的全路徑> # 對于sudo方式的運行，JAVA_HOME環境變量不能傳遞給root， # 而root用戶往往沒有配置JAVA_HOME且不方便配置， # 顯式指定jstack命令的路徑就反而顯得更方便了 show-busy-java-threads.sh -a <輸出記錄到的文件> show-busy-java-threads.sh -t <重復執行的次數> -i <重復執行的間隔秒數> # 缺省執行一次；執行間隔缺省是3秒 ############################## # 注意： ############################## # 如果Java進程的用戶 與 執行腳本的當前用戶 不同，則jstack不了這個Java進程。 # 為了能切換到Java進程的用戶，需要加sudo來執行，即可以解決： sudo show-busy-java-threads.sh ~~~ 示例： ~~~ work@dev_zz_Master 10.48.186.32 23:45:50 ~/demo > bash show-busy-java-threads.sh [1] Busy(96.2%) thread(8577/0x2181) stack of java process(8576) under user(work): "main" prio=10 tid=0x00007f0c64006800 nid=0x2181 runnable [0x00007f0c6a64a000] java.lang.Thread.State: RUNNABLE at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168) at java.util.regex.Pattern$Loop.match(Pattern.java:4295) ... at java.util.regex.Matcher.match(Matcher.java:1127) at java.util.regex.Matcher.matches(Matcher.java:502) at RegexLoad.main(RegexLoad.java:27) [2] Busy(1.5%) thread(8591/0x218f) stack of java process(8576) under user(work): "C2 CompilerThread1" daemon prio=10 tid=0x00007f0c64095800 nid=0x218f waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE [3] Busy(0.8%) thread(8590/0x218e) stack of java process(8576) under user(work): "C2 CompilerThread0" daemon prio=10 tid=0x00007f0c64093000 nid=0x218e waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE [4] Busy(0.2%) thread(8593/0x2191) stack of java process(8576) under user(work): "VM Periodic Task Thread" prio=10 tid=0x00007f0c640a2800 nid=0x2191 waiting on condition [5] Busy(0.1%) thread(25159/0x6247) stack of java process(25137) under user(work): "VM Periodic Task Thread" prio=10 tid=0x00007f13340b4000 nid=0x6247 waiting on condition work@dev_zz_Master 10.48.186.32 23:46:04 ~/demo > ~~~ 可以看到，一鍵直接定位異常代碼行 ## 線程死鎖，程序卡住 ~~~ import java.util.*; public class SimpleDeadLock extends Thread { public static Object l1 = new Object(); public static Object l2 = new Object(); private int index; public static void main(String[] a) { Thread t1 = new Thread1(); Thread t2 = new Thread2(); t1.start(); t2.start(); } private static class Thread1 extends Thread { public void run() { synchronized (l1) { System.out.println("Thread 1: Holding lock 1..."); try { Thread.sleep(10); } catch (InterruptedException e) {} System.out.println("Thread 1: Waiting for lock 2..."); synchronized (l2) { System.out.println("Thread 2: Holding lock 1 & 2..."); } } } } private static class Thread2 extends Thread { public void run() { synchronized (l2) { System.out.println("Thread 2: Holding lock 2..."); try { Thread.sleep(10); } catch (InterruptedException e) {} System.out.println("Thread 2: Waiting for lock 1..."); synchronized (l1) { System.out.println("Thread 2: Holding lock 2 & 1..."); } } } } } ~~~  一鍵定位：可以清晰的看到線程互相鎖住了對方等待的資源，導致死鎖，直接定位到代碼行和具體原因。