Tomcat性能調優 | Tomcat Performance Tuning

時間 2019-11-29

標籤 tomcat 性能 performance tuning 欄目 Tomcat 简体版

原文原文鏈接

Tomcat性能調優

修改Tomcat Connector運行模式，優化Tomcat運行性能

Tomcat Connector(Tomcat鏈接器)有bio、nio、apr三種運行模式

http://www.365mini.com/page/tomcat-connector-mode.htm
1. bio(blocking I/O)，顧名思義，即阻塞式I/O操做，表示Tomcat使用的是傳統的Java I/O操做(即java.io包及其子包)。Tomcat在默認狀況下，就是以bio模式運行的。遺憾的是，就通常而言，bio模式是三種運行模式中性能最低的一種。經過 Tomcat Manager來查看服務器的當前狀態。
http://server206:8080/manager/status
JVM
Free memory: 355.66 MB Total memory: 466.86 MB Max memory: 1016.12 MB
"ajp-apr-8009"
"http-apr-8080"
2. nio(new I/O)，是Java SE 1.4及後續版本提供的一種新的I/O操做方式(即java.nio包及其子包)。Java nio是一個基於緩衝區、並能提供非阻塞I/O操做的Java API，所以nio也被當作是non-blocking I/O的縮寫。它擁有比傳統I/O操做(bio)更好的併發運行性能。要讓Tomcat以nio模式來運行也比較簡單，咱們只須要在Tomcat安裝目錄 /conf/server.xml文件中將以下配置：
<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
中的protocol屬性值改成org.apache.coyote.http11.Http11NioProtocol便可：
<Connector port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol"
connectionTimeout="20000"
redirectPort="8443" />
此時，咱們就能夠在Tomcat Manager中看到當前服務器狀態頁面的HTTP協議的Connector運行模式已經從http-bio-8080變成了http-nio- 8080。
3. apr(Apache Portable Runtime/Apache可移植運行時)，是Apache HTTP服務器的支持庫。你能夠簡單地理解爲，Tomcat將以JNI的形式調用Apache HTTP服務器的核心動態連接庫來處理文件讀取或網絡傳輸操做，從而大大地提升Tomcat對靜態文件的處理性能。 Tomcat apr也是在Tomcat上運行高併發應用的首選模式。與配置nio運行模式同樣，也須要將對應的Connector節點的protocol屬性值改成 org.apache.coyote.http11.Http11AprProtocol。php

Tomcat官方關於三種運行模式的對比

https://tomcat.apache.org/tomcat-7.0-doc/config/http.html#Connector_Comparisonhtml

Java Blocking Connector   Java Non Blocking Connector   APR/native Connector
                                 BIO                         NIO                       APR
    Classname              Http11Protocol             Http11NioProtocol         Http11AprProtocol
    Tomcat Version           3.x onwards                 6.x onwards              5.5.x onwards
    Support Polling              NO                          YES                       YES
    Polling Size                 N/A                   maxConnections             maxConnections
    Read Request Headers      Blocking                  Non Blocking                 Blocking
    Read Request Body         Blocking                    Blocking                   Blocking
    Write Response            Blocking                    Blocking                   Blocking
    Wait for next Request     Blocking                  Non Blocking               Non Blocking
    SSL Support               Java SSL                    Java SSL                   OpenSSL
    SSL Handshake             Blocking                  Non blocking                 Blocking
    Max Connections        maxConnections              maxConnections             maxConnections

如何選擇BIO or NIO以及默認設置

https://tomcat.apache.org/tomcat-8.0-doc/config/http.htmljava

When to prefer NIO vs BIO depends on the use case.linux

If you mostly have regular request-response usage, then it doesn’t matter, and even BIO might be a better choice (as seen in my previous benchmarks).
If you have long-living connections, then NIO is the better choice, because it can server more concurrent users without the need to dedicate a blocked thread to each. The poller threads handle the sending of data back to the client, while the worker threads handle new requests. In other words, neither poller, nor worker threads are blocked and reserved by a single user.

Tomcat7和Tomcat8默認設置都是http1.1，Tomcat7默認使用BIO，Tomcat8根據狀況自動選擇BIO仍是NIO，甚至NIO2.web

The default value is always 「HTTP/1.1″, but in Tomcat 7 that 「uses an auto-switching mechanism to select either a blocking Java based connector or an APR/native based connector」, while in Tomcat 8 「uses an auto-switching mechanism to select either a non blocking Java NIO based connector or an APR/native based connector」. And to make things even harder, they introduced a NIO2 connector. And to be honest, I don’t know which one of the two NIO connectors is used by default.apache

NIO比BIO並無明顯的性能提高 centos

http://techblog.bozho.net/non-blocking-benchmark/ api

「non-blocking doesn’t have visible benefits and one should not force himself to use the possibly unfriendly callback programming model for the sake of imaginary performance gains」tomcat

使用SSL時的APR vs. NIO/BIO服務器

https://blog.eveoh.nl/2012/04/some-notes-on-tomcat-connector-performance/

Tomcat ships with 3 HTTP(s) connectors:

Blocking IO (org.apache.coyote.Http11Protocol): this is the default and most stable connector.
Non-blocking IO (org.apache.coyote.Http11NioProtocol): this is a non-blocking IO connector, which you will need for Comet/WebSockets and should offer slightly better performance in most cases.
APR (org.apache.coyote.Http11AprProtocol): this connector uses Apache Portable Runtime and OpenSSL instead of their Java counterparts. Because of this, performance is generally better, especially when using SSL.

Some conclusions we can draw from these results:

Apache Tomcat performs on a level comparable to Apache HTTPD. This is at least the case for dynamic requests, but I have seen similar results for static requests.
When using SSL: use keep-alive, unless you have a specific reason not to.
When using SSL on Tomcat: use APR.
Don’t expect NIO to give a better performance than BIO out of the box. Benchmark, benchmark, benchmark.

關於Keep-alive設置

maxKeepAliveRequests 　　　If not specified, this attribute is set to 100. 通常設置100~200.

keepAliveTimeout　　　　　　 The default value is to use the value that has been set for the connectionTimeout attribute.

NIO運行模式啓動的log

...

INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
Aug 16, 2016 1:38:31 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-nio-8080"]
Aug 16, 2016 1:38:31 PM org.apache.tomcat.util.net.NioSelectorPool getSharedSelector
INFO: Using a shared selector for servlet write/read
Aug 16, 2016 1:38:31 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-nio-8443"]
Aug 16, 2016 1:38:31 PM org.apache.tomcat.util.net.NioSelectorPool getSharedSelector
INFO: Using a shared selector for servlet write/read
Aug 16, 2016 1:38:31 PM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-bio-8009"]

...

Tomcat性能調優之線程池配置

http://jiangzhengjun.iteye.com/blog/852924
線程池配置
<Service name="Catalina">
<Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
        maxThreads="500" minSpareThreads="20" maxIdleTime="60000" /> http://zyycaesar.iteye.com/blog/299818
最大線程500（通常服務器足以），最小空閒線程數20，線程最大空閒時間60秒。
<Connector executor="tomcatThreadPool" port="8090" protocol="org.apache.coyote.http11.Http11AprProtocol"
               connectionTimeout="45000" redirectPort="8445" />
or
<Connector executor="tomcatThreadPool" port="80" protocol="HTTP/1.1"
maxThreads="600"
minSpareThreads="100"
maxSpareThreads="300"
               connectionTimeout="60000"
               keepAliveTimeout="15000"
               maxKeepAliveRequests="1"
               redirectPort="443"
               ....../>

http://192.168.1.155:8090/manager/status
默認：
JVM
    Free memory: 74.17 MB Total memory: 149.12 MB Max memory: 227.56 MB
"ajp-apr-8109"
    Max threads: 200 Current thread count: 0 Current thread busy: 0 Keeped alive sockets count: 0
     Max processing time: 0 ms Processing time: 0.0 s Request count: 0 Error count: 0 Bytes received: 0.00 MB Bytes sent: 0.00 MB

"http-apr-8090"
    Max threads: 200 Current thread count: 10 Current thread busy: 1 Keeped alive sockets count: 2
     Max processing time: 702 ms Processing time: 3.743 s Request count: 83 Error count: 3 Bytes received: 0.00 MB Bytes sent: 0.35 MB
配置線程池以後：
JVM
    Free memory: 76.36 MB Total memory: 153.81 MB Max memory: 227.56 MB
"ajp-apr-8109"
    Max threads: 200 Current thread count: 0 Current thread busy: 0 Keeped alive sockets count: 0
    Max processing time: 0 ms Processing time: 0.0 s Request count: 0 Error count: 0 Bytes received: 0.00 MB Bytes sent: 0.00 MB
"http-apr-8090"
    Max threads: 500 Current thread count: 2 Current thread busy: 1 Keeped alive sockets count: 0
    Max processing time: 0 ms Processing time: 0.0 s Request count: 0 Error count: 0 Bytes received: 0.00 MB Bytes sent: 0.00 MB

Linux下查看tomcat鏈接數
netstat -na | grep ESTAB | grep 8080 | wc -l
$ netstat -na | grep ESTAB | grep 8090 | wc -l
2
$ netstat -na | grep ESTAB | grep 8090
tcp        0      0 123.56.104.184:8090         111.205.208.29:50634        ESTABLISHED
tcp        0      0 123.56.104.184:8090         111.205.208.29:50635        ESTABLISHED
tcp        0      0 123.56.104.184:8090         111.205.208.29:50633        ESTABLISHED
查看Manager Status： "http-bio-8090"，顯示thread count爲3，是一致，以下：
Max threads: 500 Current thread count: 20 Current thread busy: 3

Tomcat性能調優之APR （Apache Portable Runtime）配置

allows Tomcat to use certain native resources for performance
http://tomcat.apache.org/native-doc/
若是沒裝啓動Tomcat時候，Catalina.out:
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
1. install APR
In rpm based Linux those dependencies could be installed by something like:
yum install apr-devel openssl-devel
==========================================================================================================================
Package                            Arch                  Version                            Repository              Size
==========================================================================================================================
Installing:
apr-devel                          x86_64                1.3.9-5.el6_2                      base                   176 k
openssl-devel                      x86_64                1.0.1e-30.el6_6.4                  updates                1.2 M
Installing for dependencies:
apr                                x86_64                1.3.9-5.el6_2                      base                   123 k
keyutils-libs-devel                x86_64                1.4-5.el6                          base                    29 k
krb5-devel                         x86_64                1.10.3-33.el6                      base                   498 k
libcom_err-devel                   x86_64                1.41.12-21.el6                     base                    32 k
libselinux-devel                   x86_64                2.0.94-5.8.el6                     base                   137 k
libsepol-devel                     x86_64                2.0.41-4.el6                       base                    64 k
zlib-devel                         x86_64                1.2.3-29.el6                       base                    44 k
Updating for dependencies:
e2fsprogs                          x86_64                1.41.12-21.el6                     base                   553 k
e2fsprogs-libs                     x86_64                1.41.12-21.el6                     base                   121 k
keyutils-libs                      x86_64                1.4-5.el6                          base                    20 k
krb5-libs                          x86_64                1.10.3-33.el6                      base                   765 k
libcom_err                         x86_64                1.41.12-21.el6                     base                    37 k
libselinux                         x86_64                2.0.94-5.8.el6                     base                   108 k
libselinux-utils                   x86_64                2.0.94-5.8.el6                     base                    82 k
libss                              x86_64                1.41.12-21.el6                     base                    41 k
openssl                            x86_64                1.0.1e-30.el6_6.4                  updates                1.5 M

Transaction Summary
==========================================================================================================================
Install       9 Package(s)
Upgrade       9 Package(s)

Total download size: 5.4 M
Is this ok [y/N]: y
Downloading Packages:
(1/18): apr-1.3.9-5.el6_2.x86_64.rpm                                                               | 123 kB     00:00
(2/18): apr-devel-1.3.9-5.el6_2.x86_64.rpm                                                         | 176 kB     00:04
(3/18): e2fsprogs-1.41.12-21.el6.x86_64.rpm                                                        | 553 kB     00:00
(4/18): e2fsprogs-libs-1.41.12-21.el6.x86_64.rpm                                                   | 121 kB     00:02
(5/18): keyutils-libs-1.4-5.el6.x86_64.rpm                                                         | 20 kB     00:00
(6/18): keyutils-libs-devel-1.4-5.el6.x86_64.rpm                                                   | 29 kB     00:00
(7/18): krb5-devel-1.10.3-33.el6.x86_64.rpm                                                        | 498 kB     00:00
(8/18): krb5-libs-1.10.3-33.el6.x86_64.rpm                                                         | 765 kB     00:00
(9/18): libcom_err-1.41.12-21.el6.x86_64.rpm                                                       | 37 kB     00:00
(10/18): libcom_err-devel-1.41.12-21.el6.x86_64.rpm                                                | 32 kB     00:00
(11/18): libselinux-2.0.94-5.8.el6.x86_64.rpm                                                      | 108 kB     00:00
(12/18): libselinux-devel-2.0.94-5.8.el6.x86_64.rpm                                                | 137 kB     00:03
(13/18): libselinux-utils-2.0.94-5.8.el6.x86_64.rpm                                                | 82 kB     00:00
(14/18): libsepol-devel-2.0.41-4.el6.x86_64.rpm                                                    | 64 kB     00:00
(15/18): libss-1.41.12-21.el6.x86_64.rpm                                                           | 41 kB     00:00
(16/18): openssl-1.0.1e-30.el6_6.4.x86_64.rpm                                                      | 1.5 MB     00:00
(17/18): openssl-devel-1.0.1e-30.el6_6.4.x86_64.rpm                                                | 1.2 MB     00:41
(18/18): zlib-devel-1.2.3-29.el6.x86_64.rpm                                                        | 44 kB     00:00
--------------------------------------------------------------------------------------------------------------------------
Total                                                                                      43 kB/s | 5.4 MB     02:09

[root@iZ94gt8lzgnZ logs]# rpm -ql apr
/usr/lib64/libapr-1.so.0
/usr/lib64/libapr-1.so.0.3.9
/usr/share/doc/apr-1.3.9
/usr/share/doc/apr-1.3.9/CHANGES
/usr/share/doc/apr-1.3.9/LICENSE
/usr/share/doc/apr-1.3.9/NOTICE

[root@iZ94gt8lzgnZ native]# rpm -ql apr-devel
/usr/bin/apr-1-config
/usr/include/apr-1
/usr/include/apr-1/apr-x86_64.h
/usr/include/apr-1/apr.h
/usr/include/apr-1/apr_allocator.h
/usr/include/apr-1/apr_atomic.h
/usr/include/apr-1/apr_dso.h
/usr/include/apr-1/apr_env.h
/usr/include/apr-1/apr_errno.h
/usr/include/apr-1/apr_file_info.h
/usr/include/apr-1/apr_file_io.h
/usr/include/apr-1/apr_fnmatch.h
/usr/include/apr-1/apr_general.h
/usr/include/apr-1/apr_getopt.h
/usr/include/apr-1/apr_global_mutex.h
/usr/include/apr-1/apr_hash.h
/usr/include/apr-1/apr_inherit.h
/usr/include/apr-1/apr_lib.h
/usr/include/apr-1/apr_mmap.h
/usr/include/apr-1/apr_network_io.h
/usr/include/apr-1/apr_poll.h
/usr/include/apr-1/apr_pools.h
/usr/include/apr-1/apr_portable.h
/usr/include/apr-1/apr_proc_mutex.h
/usr/include/apr-1/apr_random.h
/usr/include/apr-1/apr_ring.h
/usr/include/apr-1/apr_shm.h
/usr/include/apr-1/apr_signal.h
/usr/include/apr-1/apr_strings.h
/usr/include/apr-1/apr_support.h
/usr/include/apr-1/apr_tables.h
/usr/include/apr-1/apr_thread_cond.h
/usr/include/apr-1/apr_thread_mutex.h
/usr/include/apr-1/apr_thread_proc.h
/usr/include/apr-1/apr_thread_rwlock.h
/usr/include/apr-1/apr_time.h
/usr/include/apr-1/apr_user.h
/usr/include/apr-1/apr_version.h
/usr/include/apr-1/apr_want.h
/usr/lib64/apr-1
/usr/lib64/apr-1/build
/usr/lib64/apr-1/build/apr_rules.mk
/usr/lib64/apr-1/build/libtool
/usr/lib64/apr-1/build/make_exports.awk
/usr/lib64/apr-1/build/make_var_export.awk
/usr/lib64/apr-1/build/mkdir.sh
/usr/lib64/libapr-1.la
/usr/lib64/libapr-1.so
/usr/lib64/pkgconfig/apr-1.pc
/usr/share/aclocal/find_apr.m4
/usr/share/doc/apr-devel-1.3.9
/usr/share/doc/apr-devel-1.3.9/APRDesign.html
/usr/share/doc/apr-devel-1.3.9/canonical_filenames.html
/usr/share/doc/apr-devel-1.3.9/incomplete_types
/usr/share/doc/apr-devel-1.3.9/non_apr_programs

http://wander312.iteye.com/blog/1132975
/usr/lib64已經在path裏面了，不用加了：
vi /etc/profile
# 後面添加如下內容
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/lib64
# 使profile生效，
source /etc/profile
2. install Tomcat Native Connector
wget http://mirrors.cnnic.cn/apache/tomcat/tomcat-connectors/native/1.1.32/source/tomcat-native-1.1.32-src.tar.gz
tar zxvf tomcat-native-1.1.32-src.tar.gz
cd tomcat-native-1.1.32-src/jni/native
./configure --with-apr=/usr/bin/apr-1-config --with-java-home=/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.65.x86_64 --with-ssl=/usr/bin/openssl --prefix=/root/apache-tomcat-7.0.57

[root@iZ94gt8lzgnZ ~]# ls /usr/lib/jvm
java-1.7.0-openjdk-1.7.0.65.x86_64 jre jre-1.7.0 jre-1.7.0-openjdk.x86_64 jre-openjdk
[root@iZ94gt8lzgnZ native]# ls /usr/bin/open*
/usr/bin/open /usr/bin/openssl /usr/bin/openvt

3. 啓動 tomcat 後，看日誌：
bin/startup.sh
head logs/catalina.out
能夠看到如下結果：
信息: Loaded APR based Apache Tomcat Native library 1.1.14.
2009-1-13 11:12:51 org.apache.catalina.core.AprLifecycleListener init
信息: APR capabilities: IPv6 [true], sendfile [true], accept filters [false], random [true].

Linux下查看tomcat鏈接數
netstat -na | grep ESTAB | grep 8080 | wc -l
$ netstat -na | grep ESTAB | grep 8090 | wc -l
2
$ netstat -na | grep ESTAB | grep 8090
tcp        0      0 123.56.104.184:8090         111.205.208.29:50634        ESTABLISHED
tcp        0      0 123.56.104.184:8090         111.205.208.29:50635        ESTABLISHED
tcp        0      0 123.56.104.184:8090         111.205.208.29:50633        ESTABLISHED
查看Manager Status： "http-bio-8090"，顯示thread count爲3，是一致，以下：
Max threads: 500 Current thread count: 20 Current thread busy: 3

Tomcat JVM性能調優

關於JVM

整個JVM內存大小=年輕代大小 + 年老代大小 + 持久代大小.(1536+512=2g)

Sun官方推薦年輕代配置爲整個堆的3/8。

JVM內存構成說明

JVM Heap memory elements	JVM Non-Heap memory parts
Eden Space: The pool from which memory is initially allocated for most objects.	Permanent Generation: The pool containing all the reflective data of the virtual machine itself, such as class and method objects. With Java VMs that use class data sharing, this generation is divided into read-only and read-write areas.
Survivor Space: The pool containing objects that have survived the garbage collection of the Eden space. This space is divided to ‘From Space’ and ‘To Space’ (for example in jmap output).	Code Cache: The HotSpot Java VM also includes a code cache, containing memory that is used for compilation and storage of native code.
Tenured Generation/PS Old Gen: The pool containing objects that have existed for some time in the survivor space.

JVM內存構成圖解

Below diagram illustrates JVM memory parts and JVM (java) related command line switches used to preset/limit some of them.

- See more at: http://www.jvmhost.com/articles/how-can-i-monitor-memory-usage-of-my-tomcat-jvm#sthash.Ctd36Kca.dpuf

NewRatio在不一樣平臺的推薦值

https://blogs.oracle.com/jonthecollector/entry/the_second_most_important_gc

If your application has a large proportion of long lived data, the value of NewRatio may not put enough of the space into the tenured generation.

Something to add here is that the default value of NewRatio is platform dependent and runtime compiler (JIT) dependent. Below are the values as we get ready for the JDK6 release.

-server on amd64 2

-server on ia32 8

-server on sparc 2

-client on ia32 12

-client on sparc 8

IBM的Heap Analyser

G1GC

JDK7新特性之

http://dongliu.net/post/404142

Garbage-first garbage collector，簡稱G1 GC，是最終將用於代替Concurrent Mark-Sweep garbage collector(CMS GC)的新一代垃圾回收器。

目前JDK1.6update14及之後版本的jvm中已經繼承了G1 GC，可使用參數-XX:+UnlockExperimentalVMOptions -XX:+UseG1GC來啓用。

https://blogs.oracle.com/g1gc/

JVM內存限制(最大值)

在命令行下用 java -XmxXXXXM -version 命令來進行測試，而後逐漸的增大XXXX的值，若是執行正常就表示指定的內存大小可用，不然會打印錯誤信息。

http://unixboy.iteye.com/blog/174173

Tomcat JVM 調優記錄

Tomcat 20150616配置和狀態

整個JVM內存大小=年輕代大小 + 年老代大小 + 持久代大小

Note：Tomcat從20150604啓動，20150612 reload DDTService。

$ cat /opt/tomcat-ddtservice/bin/setenv.sh

export JAVA_OPTS="-Dfile.encoding=UTF-8 -Xms512m -Xmx2048m -XX:PermSize=128m -XX:MaxPermSize=768m"

admin@.184:~]

$ ps -auxw --sort=%cpu

USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND

root 17733 0.1 0.1 991520 10048 ? Sl May20 76:51 /usr/local/aegis/alihids/AliHids

root 18847 0.2 0.1 793852 13936 ? Sl Apr03 249:44 /usr/local/aegis/aegis_client/aegis_00_73/AliYunDun

admin 20880 0.8 33.3 5557668 2686652 ? Sl Jun04 146:14 /opt/jdk1.7.0_71/bin/java -Djava.util.logging.config.file=/opt/tomca

admin 2480 3.0 7.2 3926212 584256 ? Sl Jan06 7151:06 /opt/jdk1.7.0_71/bin/java -Djava.util.logging.config.file=/opt/apac

admin@.184:~]

$ free

total used free shared buffers cached

Mem: 8058260 7873136 185124 0 149520 4179732

-/+ buffers/cache: 3543884 4514376

Swap: 0 0 0

http://.28:8161/admin/subscribers.jsp

Active Durable Topic Subscribers

http://.184:8090/manager/status

*Server Information*
Tomcat Version	JVM Version	JVM Vendor	OS Name	OS Version	OS Architecture	Hostname	IP Address
Apache Tomcat/7.0.57	1.7.0_71-b14	Oracle Corporation	Linux	2.6.32-358.6.2.el6.x86_64	amd64	iZ25f12r4xgZ	10.170.207.50

"ajp-bio-8209"

Max threads: 200 Current thread count: 0 Current thread busy: 0
Max processing time: 0 ms Processing time: 0.0 s Request count: 0 Error count: 0 Bytes received: 0.00 MB Bytes sent: 0.00 MB

"http-bio-8090"

Max threads: 500 Current thread count: 28 Current thread busy: 18
Max processing time: 1320993 ms Processing time: 24161.775 s Request count: 380932 Error count: 63077 Bytes received: 55.11 MB Bytes sent: 3862.71 MB

JVM

Free memory: 1377.64 MB Total memory: 1899.50 MB Max memory: 1899.50 MB

Memory Pool	Type	Initial	Total	Maximum	Used
PS Eden Space	Heap memory	129.00 MB	530.50 MB	674.50 MB	26.95 MB (3%)
PS Old Gen	Heap memory	341.50 MB	1365.00 MB	1365.00 MB	446.50 MB (32%)
PS Survivor Space	Heap memory	21.00 MB	4.00 MB	4.00 MB	0.00 MB (0%)
Code Cache	Non-heap memory	2.43 MB	45.37 MB	48.00 MB	44.79 MB (93%)
PS Perm Gen	Non-heap memory	128.00 MB	310.00 MB	768.00 MB	309.57 MB (40%)

Tomcat 20150616 問題

系統剩餘內存太少。（185M）
Code Cache used太高，接近上限。（ReservedCodeCacheSize and InitialCodeCacheSize）
PS Perm Gen（Permanent Generation）只用到一半不到，基本不會再增加。
Heap memory整體使用不到一半。
服務器通常設置-Xms、-Xmx相等以免在每次GC 後調整堆的大小。

Tomcat 20150616 調整

export JAVA_OPTS="-Dfile.encoding=UTF-8 -Xms512m -Xmx2048m -XX:PermSize=128m -XX:MaxPermSize=768m"

調整爲：

export JAVA_OPTS="-Dfile.encoding=UTF-8 –Xms1024m -Xmx1536m -XX:PermSize=256m -XX:MaxPermSize=512m -XX:ReservedCodeCacheSize=128m"

Tomcat 20150616 調整後跟蹤

20150618上線以後測試完畢22：00

JVM

Free memory: 1245.49 MB Total memory: 1436.00 MB Max memory: 1436.00 MB

Memory Pool	Type	Initial	Total	Maximum	Used
PS Eden Space	Heap memory	384.00 MB	311.50 MB	311.50 MB	61.70 MB (19%)
PS Old Gen	Heap memory	1024.00 MB	1024.00 MB	1024.00 MB	121.35 MB (11%)
PS Survivor Space	Heap memory	64.00 MB	100.50 MB	100.50 MB	7.44 MB (7%)
Code Cache	Non-heap memory	2.43 MB	9.43 MB	128.00 MB	9.24 MB (7%)
PS Perm Gen	Non-heap memory	256.00 MB	256.00 MB	512.00 MB	74.74 MB (14%)

20150619上線以後測試完畢16：47

JVM

Free memory: 1199.51 MB Total memory: 1508.50 MB Max memory: 1508.50 MB

Memory Pool	Type	Initial	Total	Maximum	Used
PS Eden Space	Heap memory	384.00 MB	456.50 MB	456.50 MB	53.91 MB (11%)
PS Old Gen	Heap memory	1024.00 MB	1024.00 MB	1024.00 MB	247.09 MB (24%)
PS Survivor Space	Heap memory	64.00 MB	28.00 MB	28.00 MB	7.96 MB (28%)
Code Cache	Non-heap memory	2.43 MB	19.62 MB	128.00 MB	18.88 MB (14%)
PS Perm Gen	Non-heap memory	256.00 MB	256.00 MB	512.00 MB	98.51 MB (19%)

20150629 10:30(6月19日晚上重啓過)上線後10天

JVM

Free memory: 1180.61 MB Total memory: 1470.50 MB Max memory: 1470.50 MB

Memory Pool	Type	Initial	Total	Maximum	Used
PS Eden Space	Heap memory	384.00 MB	420.00 MB	439.00 MB	16.91 MB (3%)
PS Old Gen	Heap memory	1024.00 MB	1024.00 MB	1024.00 MB	246.81 MB (24%)
PS Survivor Space	Heap memory	64.00 MB	26.50 MB	26.50 MB	26.15 MB (98%)
Code Cache	Non-heap memory	2.43 MB	27.00 MB	128.00 MB	26.58 MB (20%)
PS Perm Gen	Non-heap memory	256.00 MB	256.00 MB	512.00 MB	121.63 MB (23%)

20150629 10:33

Free memory: 972.35 MB Total memory: 1492.00 MB Max memory: 1492.00 MB

Memory Pool	Type	Initial	Total	Maximum	Used
PS Eden Space	Heap memory	384.00 MB	421.50 MB	421.50 MB	274.89 MB (65%)
PS Old Gen	Heap memory	1024.00 MB	1024.00 MB	1024.00 MB	244.74 MB (23%)
PS Survivor Space	Heap memory	64.00 MB	46.50 MB	46.50 MB	0.00 MB (0%)
Code Cache	Non-heap memory	2.43 MB	27.00 MB	128.00 MB	26.59 MB (20%)
PS Perm Gen	Non-heap memory	256.00 MB	256.00 MB	512.00 MB	121.57 MB (23%)

整個JVM內存大小=年輕代大小 + 年老代大小 + 持久代大小.(1536+512=2g)

Sun官方推薦年輕代配置爲整個堆的3/8。

-Xmn2g：設置年輕代大小爲2G。

-XX:NewRatio=4:設置年輕代（包括Eden和兩個Survivor區）與年老代的比值（除去持久代）。設置爲4，則年輕代與年老代所佔比值爲1：4，年輕代佔整個堆棧的1/5

-XX:SurvivorRatio=4：設置年輕代中Eden區與Survivor區的大小比值。設置爲4，則兩個Survivor區與一個Eden區的比值爲2:4，一個Survivor區佔整個年輕代的1/6

-Xss128k：設置每一個線程的堆棧大小。JDK5.0之後每一個線程堆棧大小爲1M，之前每一個線程堆棧大小爲256K。

-XX:NewRation=1設爲1是由於PS Eden Space上下浮動很大，同時PS Old Gen卻無變化，說明建立了不少新對象以後很快被回收；所以應該調大Eden Space.

Tomcat 再次調整

export JAVA_OPTS="-Dfile.encoding=UTF-8 -Xms512m -Xmx2048m -XX:PermSize=128m -XX:MaxPermSize=768m"

調整爲：

export JAVA_OPTS="-Dfile.encoding=UTF-8 -Xms1024m -Xmx1536m -XX:PermSize=256m -XX:MaxPermSize=512m -XX:ReservedCodeCacheSize=128m"

調整爲：

export JAVA_OPTS="-Dfile.encoding=UTF-8 -Xms1536m -Xmx1536m -XX:NewRatio=1 -XX:PermSize=256m -XX:MaxPermSize=512m -XX:ReservedCodeCacheSize=128m –Xss256k "

export JAVA_OPTS="-Dfile.encoding=UTF-8 -Xms1536m -Xmx1536m -XX:NewRatio=1 -XX:SurvivorRatio=6 -XX:PermSize=256m -XX:MaxPermSize=512m -Xss256k -XX:ReservedCodeCacheSize=128m "

tomcat+java的web程序持續佔cpu問題調試

解決方法：
一、先用top查看佔用cpu的進程id
二、再用ps -ef | grep PID定位具體的進程主體；如是不是tomcat啓動的java程序
三、用ps -mp pid -o THREAD,tid,time打印出該進程下的線程佔用cpu狀況
       找到了耗時最高的線程28802，佔用CPU時間快兩個小時了！
四、其次將須要的線程ID轉換爲16進制格式：printf "%x\n" tid
五、最後打印線程的堆棧信息：jstack pid | grep tid -A 30
       找到出現問題的代碼，並分析具體函數中是否有可能出現死循環的代碼段。
       一般問題出如今while， for之類的循環代碼片斷。

jstack command not found on centos
[root@yfddt5Z logs]# sudo updatedb
[root@yfddt5Z logs]# locate jstack
/usr/java/jdk1.7.0_79/bin/jstack
/usr/java/jdk1.7.0_79/man/ja_JP.UTF-8/man1/jstack.1
/usr/java/jdk1.7.0_79/man/man1/jstack.1