背景
最近被问到一个问题：==如何看某一个类的性能？==
当时一紧张只想起有火焰图这个概念，却不知还有强大的线上诊断工具Arthas。
纸上得来终觉浅，绝知此事要躬行。
实战
启动demo
curl -O https://alibaba.github.io/arthas/arthas-demo.jar
java -jar arthas-demo.jar
arthas-demo是一个简单的程序，每隔一秒生成一个随机数，再执行质因数分解，并打印出分解结果。
下载安装
wget https://alibaba.github.io/arthas/arthas-boot.jar
安装结果
bash-3.2$ wget https://alibaba.github.io/arthas/arthas-boot.jar
--2020-04-12 17:13:51-- https://alibaba.github.io/arthas/arthas-boot.jar
正在解析主机 alibaba.github.io (alibaba.github.io)... 185.199.109.153, 185.199.110.153, 185.199.111.153, ...
正在连接 alibaba.github.io (alibaba.github.io)|185.199.109.153|:443... 失败：Operation timed out。
正在连接 alibaba.github.io (alibaba.github.io)|185.199.110.153|:443... 已连接。
已发出 HTTP 请求，正在等待回应... 200 OK
长度：112288 (110K) [application/java-archive]
正在保存至: “arthas-boot.jar”
arthas-boot.jar 100%[==============================================================================================>] 109.66K 21.8KB/s 用时 5.0s
2020-04-12 17:15:18 (21.8 KB/s) - 已保存 “arthas-boot.jar” [112288/112288])
启动Arthas
java -jar arthas-boot.jar
启动结果
bash-3.2$ java -jar arthas-boot.jar
[INFO] arthas-boot version: 3.2.0
[INFO] Found existing java process, please choose one and input the serial number of the process, eg : 1. Then hit ENTER.
* [1]: 20768 arthas-demo.jar
[2]: 20791
[3]: 20807 org.jetbrains.jps.cmdline.Launcher
[4]: 20814 org.jetbrains.idea.maven.server.RemoteMavenServer36
1
[INFO] Start download arthas from remote server: https://maven.aliyun.com/repository/public/com/taobao/arthas/arthas-packaging/3.2.0/arthas-packaging-3.2.0-bin.zip
[INFO] File size: 10.82 MB, downloaded size: 423.37 KB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 1.19 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 1.81 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 2.71 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 3.76 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 4.88 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 6.04 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 7.32 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 8.52 MB, downloading ...
[INFO] File size: 10.82 MB, downloaded size: 10.02 MB, downloading ...
[INFO] Download arthas success.
[INFO] arthas home: /Users/XXX/.arthas/lib/3.2.0/arthas
[INFO] Try to attach process 20768
[INFO] Attach process 20768 success.
[INFO] arthas-client connect 127.0.0.1 3658
,---. ,------. ,--------.,--. ,--. ,---. ,---.
/ O \ | .--. ''--. .--'| '--' | / O \ ' .-'
| .-. || '--'.' | | | .--. || .-. |`. `-.
| | | || |\ \ | | | | | || | | |.-' |
`--' `--'`--' '--' `--' `--' `--'`--' `--'`-----'
wiki https://alibaba.github.io/arthas
tutorials https://alibaba.github.io/arthas/arthas-tutorials
version 3.2.0
pid 20768
time 2020-04-12 17:34:38
dashboard
[arthas@20768]$ dashboard
ID NAME GROUP PRIORITY STATE %CPU TIME INTERRUPT DAEMON
30 Timer-for-arthas-dashboard-de4 system 10 RUNNABLE 100 0:0 false true
11 Attach Listener system 9 RUNNABLE 0 0:0 false true
10 Common-Cleaner InnocuousThreadGroup 8 TIMED_WAIT 0 0:0 false true
3 Finalizer system 8 WAITING 0 0:0 false true
2 Reference Handler system 10 RUNNABLE 0 0:0 false true
4 Signal Dispatcher system 9 RUNNABLE 0 0:0 false true
16 arthas-shell-server system 9 TIMED_WAIT 0 0:0 false true
29 as-command-execute-daemon system 10 TIMED_WAIT 0 0:0 false true
13 job-timeout system 9 TIMED_WAIT 0 0:0 false true
1 main main 5 TIMED_WAIT 0 0:0 false false
14 nioEventLoopGroup-2-1 system 10 RUNNABLE 0 0:0 false false
19 nioEventLoopGroup-2-2 system 10 RUNNABLE 0 0:0 false false
23 nioEventLoopGroup-2-3 system 10 RUNNABLE 0 0:0 false false
24 nioEventLoopGroup-2-4 system 10 RUNNABLE 0 0:0 false false
25 nioEventLoopGroup-2-5 system 10 RUNNABLE 0 0:0 false false
26 nioEventLoopGroup-2-6 system 10 RUNNABLE 0 0:0 false false
27 nioEventLoopGroup-2-7 system 10 RUNNABLE 0 0:0 false false
Memory used total max usage GC
heap 63M 130M 2048M 3.08% gc.g1_young_generation.count 2
g1_eden_space 52M 70M -1 74.29% gc.g1_young_generation.time(ms) 30
g1_old_gen 1M 50M 2048M 0.06% gc.g1_old_generation.count 0
g1_survivor_space 10M 10M -1 100.00% gc.g1_old_generation.time(ms) 0
nonheap 24M 28M -1 85.73%
codeheap_'non-nmethods' 1M 2M 5M 20.44%
metaspace 16M 17M -1 95.36%
Runtime
os.name Mac OS X
os.version 10.15.3
java.version 12.0.2
java.home /Library/Java/JavaVirtualMachines/jdk-12.0.2.jdk/Contents/Home
systemload.average 2.96
processors 4
uptime 3282s
thread
[arthas@20768]$ thread
Threads Total: 13, NEW: 0, RUNNABLE: 7, BLOCKED: 0, WAITING: 2, TIMED_WAITING: 4, TERMINATED: 0
ID NAME GROUP PRIORITY STATE %CPU TIME INTERRUPT DAEMON
20 as-command-execute-daemon system 10 RUNNABLE 100 0:0 false true
11 Attach Listener system 9 RUNNABLE 0 0:0 false true
10 Common-Cleaner InnocuousThreadGroup 8 TIMED_WAIT 0 0:0 false true
3 Finalizer system 8 WAITING 0 0:0 false true
2 Reference Handler system 10 RUNNABLE 0 0:0 false true
4 Signal Dispatcher system 9 RUNNABLE 0 0:0 false true
16 arthas-shell-server system 9 TIMED_WAIT 0 0:0 false true
13 job-timeout system 9 TIMED_WAIT 0 0:0 false true
1 main main 5 TIMED_WAIT 0 0:0 false false
14 nioEventLoopGroup-2-1 system 10 RUNNABLE 0 0:0 false false
19 nioEventLoopGroup-2-2 system 10 RUNNABLE 0 0:0 false false
15 nioEventLoopGroup-3-1 system 10 RUNNABLE 0 0:0 false false
17 pool-1-thread-1 system 5 WAITING 0 0:0 false false
Affect(row-cnt:0) cost in 123 ms.
[arthas@20768]$ thread 1
"main" Id=1 TIMED_WAITING
at java.base@12.0.2/java.lang.Thread.sleep(Native Method)
at java.base@12.0.2/java.lang.Thread.sleep(Thread.java:340)
at java.base@12.0.2/java.util.concurrent.TimeUnit.sleep(TimeUnit.java:446)
at app//demo.MathGame.main(MathGame.java:17)
Affect(row-cnt:0) cost in 31 ms.
jvm
[arthas@20768]$ jvm
RUNTIME
-------------------------------------------------------------------------------------------------------------------------------
MACHINE-NAME 20768@PengdeMacBook-Pro.local
JVM-START-TIME 2020-04-12 16:54:03
MANAGEMENT-SPEC-VERSION 2.0
SPEC-NAME Java Virtual Machine Specification
SPEC-VENDOR Oracle Corporation
SPEC-VERSION 12
VM-NAME Java HotSpot(TM) 64-Bit Server VM
VM-VENDOR Oracle Corporation
VM-VERSION 12.0.2+10
INPUT-ARGUMENTS []
CLASS-PATH arthas-demo.jar
BOOT-CLASS-PATH
LIBRARY-PATH /Users/XXX/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java
/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.
-------------------------------------------------------------------------------------------------------------------------------
CLASS-LOADING
-------------------------------------------------------------------------------------------------------------------------------
LOADED-CLASS-COUNT 3030
TOTAL-LOADED-CLASS-COUNT 3030
UNLOADED-CLASS-COUNT 0
IS-VERBOSE false
-------------------------------------------------------------------------------------------------------------------------------
COMPILATION
-------------------------------------------------------------------------------------------------------------------------------
NAME HotSpot 64-Bit Tiered Compilers
TOTAL-COMPILE-TIME 4111(ms)
-------------------------------------------------------------------------------------------------------------------------------
GARBAGE-COLLECTORS
-------------------------------------------------------------------------------------------------------------------------------
G1 Young Generation 2/30(ms)
[count/time]
G1 Old Generation 0/0(ms)
[count/time]
-------------------------------------------------------------------------------------------------------------------------------
MEMORY-MANAGERS
-------------------------------------------------------------------------------------------------------------------------------
CodeCacheManager CodeHeap 'non-nmethods'
CodeHeap 'profiled nmethods'
CodeHeap 'non-profiled nmethods'
Metaspace Manager Metaspace
Compressed Class Space
G1 Young Generation G1 Eden Space
G1 Survivor Space
G1 Old Gen
G1 Old Generation G1 Eden Space
G1 Survivor Space
G1 Old Gen
-------------------------------------------------------------------------------------------------------------------------------
MEMORY
-------------------------------------------------------------------------------------------------------------------------------
HEAP-MEMORY-USAGE 136314880(130.0 MiB)/134217728(128.0 MiB)/2147483648(2.0 GiB)/45232224(43.1 MiB)
[committed/init/max/used]
NO-HEAP-MEMORY-USAGE 24444928(23.3 MiB)/7667712(7.3 MiB)/-1(-1 B)/20339320(19.4 MiB)
[committed/init/max/used]
PENDING-FINALIZE-COUNT 0
-------------------------------------------------------------------------------------------------------------------------------
OPERATING-SYSTEM
-------------------------------------------------------------------------------------------------------------------------------
OS Mac OS X
ARCH x86_64
PROCESSORS-COUNT 4
LOAD-AVERAGE 2.65380859375
VERSION 10.15.3
-------------------------------------------------------------------------------------------------------------------------------
THREAD
-------------------------------------------------------------------------------------------------------------------------------
COUNT 13
DAEMON-COUNT 8
PEAK-COUNT 13
STARTED-COUNT 16
DEADLOCK-COUNT 0
-------------------------------------------------------------------------------------------------------------------------------
FILE-DESCRIPTOR
-------------------------------------------------------------------------------------------------------------------------------
MAX-FILE-DESCRIPTOR-COUNT -1
OPEN-FILE-DESCRIPTOR-COUNT -1
Affect(row-cnt:0) cost in 243 ms.
