程序设计 – 第2页 – PHPor 的Blog

PHP 中执行命令的几种方式比较

4,286

4月 042017

system/exec 函数:

这两个函数会利用/bin/sh 指定的shell来执行指定的命令，所以，指定的命令实际上不仅可以包含可以执行的命令和参数，还可以是对应shell的内置命令以及shell支持的控制结构。

缺点：无法区分标准输出与标准错误

注意：这两个函数执行的外部命令默认继承了php进程的标准输入、标准输出和标准错误，你可以通过返回值得到进程的标准输出，但是标准错误却悄悄地流进了php进程定义的标准错误输出里面去了；更加隐晦的是，对于php-fpm进程来讲，该外部进程也默认listen（继承来的）了php-fpm监听的端口，但是肯定不会去处理php-fpm请求，一般情况下不会有问题，特殊情况下回让你莫名其妙

pcntl_exec 函数：

该函数会取代当前执行的进程空间，而且是不会再回到当前进程空间，可能你很少会用到该函数，但是，当你确实需要该函数的时候，却又是没有其他函数可以替代的，如：

# php -d error_log="" -r 'pcntl_exec("/bin/sleep", array(1));echo 2;'

1	# php -d error_log="" -r 'pcntl_exec("/bin/sleep", array(1));echo 2;'

echo 2 是不可能被执行到的

注意： pcntl_exec不同于其他函数，并不会使用shell来执行指定的命令，而且指定的命令需要是要执行的可执行文件的全路径

proc_open 函数：

这个是我最喜欢的函数：

可以通过proc_close得到外部进程的返回值
可以定义外部进程的标准输入、标准输出、标准错误，并且可以区分外部进程的标准输出和标准错误
一定程度上还可以实现并行执行多个外部命令

proc_open 示例：

<?php
$descriptorspec = array(
   0 => array("pipe", "r"),  // stdin is a pipe that the child will read from
   1 => array("pipe", "w"),  // stdout is a pipe that the child will write to
   2 => array("pipe", "w") // stderr is a file to write to
);

$cwd = '/tmp';
$env = array('some_option' => 'aeiou');

$process = proc_open('ssh -i /home/phpor/.ssh/id_rsa phpor@localhost ', $descriptorspec, $pipes, $cwd, $env);
if (is_resource($process)) {
    // $pipes now looks like this:
    // 0 => writeable handle connected to child stdin
    // 1 => readable handle connected to child stdout
    // Any error output will be appended to /tmp/error-output.txt

    fwrite($pipes[0], $argv[1]);
    fclose($pipes[0]);

    echo stream_get_contents($pipes[1]);
    fclose($pipes[1]);

    echo stream_get_contents($pipes[2]);
    fclose($pipes[2]);

    // It is important that you close any pipes before calling
    // proc_close in order to avoid a deadlock
    $return_value = proc_close($process);

    echo "command returned $return_value\n";
}

<?php

$descriptorspec = array(

0 => array("pipe", "r"), // stdin is a pipe that the child will read from

1 => array("pipe", "w"), // stdout is a pipe that the child will write to

2 => array("pipe", "w") // stderr is a file to write to

);

$cwd = '/tmp';

$env = array('some_option' => 'aeiou');

$process = proc_open('ssh -i /home/phpor/.ssh/id_rsa phpor@localhost ', $descriptorspec, $pipes, $cwd, $env);

if (is_resource($process)) {

// $pipes now looks like this:

// 0 => writeable handle connected to child stdin

// 1 => readable handle connected to child stdout

// Any error output will be appended to /tmp/error-output.txt

fwrite($pipes[0], $argv[1]);

fclose($pipes[0]);

echo stream_get_contents($pipes[1]);

fclose($pipes[1]);

echo stream_get_contents($pipes[2]);

fclose($pipes[2]);

// It is important that you close any pipes before calling

// proc_close in order to avoid a deadlock

$return_value = proc_close($process);

echo "command returned $return_value\n";

}

原文链接：https://phpor.net/blog/post/4899

golang IDE之 gogland

go No Responses »

2,039

2月 052017

https://www.jetbrains.com/go/

优点：

可以debug

原文链接：https://phpor.net/blog/post/4604

golang 可以用于windows编程吗

go No Responses »

3,166

2月 052017

golang 可以用于windows编程吗？

理论上可以，但是又有哪个IDE去支持golang进行windows编程并且能和visual studio相媲美呢？

每种语言都有他自己的用武之地，没有哪个语言可以独步天下，称霸武林的。

原文链接：https://phpor.net/blog/post/4602

关于C语言之字符串拼接（堆与栈）

C/C++ No Responses »

5,608

12月 092016

且看一个demo:

int do_sth(int type) {
    char *errstr;
    
    switch(type) {
    case 1:
        errstr = "Error";break
    case 2:
        errstr = "Warn";break
    case 3:
        errstr = "Info";break
    case 4:
        errstr = "Debug";break
    default:
        return 0;
    }

    if (...) {..}
    if (...) {
        ..;
        fprintf(stdout, "%s %s", errstr, ...);
        return 1;
    }
    if (...) { return 1;}
    if (...) {
        fprintf(stderr, "%s %s", errstr, ...);
    }
    ...
    return 0;
}

int do_sth(int type) {

char *errstr;

switch(type) {

case 1:

errstr = "Error";break

case 2:

errstr = "Warn";break

case 3:

errstr = "Info";break

case 4:

errstr = "Debug";break

default:

return 0;

}

if (...) {..}

if (...) {

..;

fprintf(stdout, "%s %s", errstr, ...);

return 1;

}

if (...) { return 1;}

if (...) {

fprintf(stderr, "%s %s", errstr, ...);

}

...

return 0;

}

问题：如何在errstr信息前面添加一个HOSTNAME 环境变量信息？

考虑到errstr有可能写到标准错误，也有可能写到标准输出，也有可能根本就不输出，所以，提前输出HOSTNAME 信息显然不合适
考虑到引用errstr的地方确实不少，最好一开始就拼接HOSTNAME到该errstr 上面去，那么如何拼接呢？

如果是在脚本语言或者带有gc的语言中，完全可以直接在errstr变量前面拼接那个动态获取到的环境变量，如：

errstr=getenv("HOSTNAME") + errstr ;

1	errstr=getenv("HOSTNAME") + errstr ;

但是c中却不能这样，为什么呢？字符串拼接的函数不是有的吗，如：strcat；

事实却并非如此简单，为什么呢？

上面的errstr变量是存储在栈上的，不需要考虑free的问题，原作者考虑到后续一大堆复杂的if分支，如果把errstr放在堆上，处处要考虑是不是该把errstr free掉，得死多少脑细胞啊！

对于HOSTNAME是个运行时的信息，显然没法放到栈上，如果非要和errstr拼接起来的话，errstr必须在堆上，即要动态的malloc，由此可见，对于脚本语言来讲，一个非常简单的逻辑，在C中却如此的麻烦

解决办法：

为了既不需要free，又能拼接字符串，可以定义一个字符数组，如： errstr[255]，然后，把需要的信息加进去；为了避免信息太多而不小心越界，可以使用snprintf函数，自动丢弃超长的部分

原文链接：https://phpor.net/blog/post/4404

关于php-fpm reload的优雅实现

PHP No Responses »

4,232

12月 082016

我们知道，nginx的reload是不会影响服务的，php-fpm也有reload 功能，而且确实不是restart，但是却是影响服务的，下面给出一种改进方式，是的php-fpm的reload不影响服务

修改源代码：

重写init脚本：

#! /bin/sh

### BEGIN INIT INFO
# Provides:          php-fpm
# Required-Start:    $remote_fs $network
# Required-Stop:     $remote_fs $network
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: starts php-fpm
# Description:       starts the PHP FastCGI Process Manager daemon
### END INIT INFO

php_fpm_BIN=/usr/sbin/php-fpm
php_fpm_CONF=/etc/php/php-fpm.conf
php_fpm_PID=/var/run/php-fpm.pid
tmp_pid=/var/run/php-fpm.tmp.pid


php_opts="--fpm-config $php_fpm_CONF --pid $tmp_pid"


wait_for_pid () {
	local pid=$1
	while kill -0 $pid >/dev/null 2>&1 ; do
		sleep 1;
	done
}

case "$1" in
	start)
		echo -n "Starting php-fpm "

		$php_fpm_BIN --daemonize $php_opts

		if [ "$?" != 0 ] ; then
			echo " failed"
			exit 1
		fi
		cat $tmp_pid >$php_fpm_PID
		echo " done"
	;;

	stop)
		echo -n "Gracefully shutting down php-fpm "

		if [ ! -r $php_fpm_PID ] ; then
			echo "warning, no pid file found - php-fpm is not running ?"
			exit 1
		fi
		pid=$(cat $php_fpm_PID)
		kill -QUIT $pid

		wait_for_pid $pid

		echo " done"
	;;

	status)
		if [ ! -r $php_fpm_PID ] ; then
			echo "php-fpm is stopped"
			exit 0
		fi

		PID=`cat $php_fpm_PID`
		if ps -p $PID | grep -q $PID; then
			echo "php-fpm (pid $PID) is running..."
		else
			echo "php-fpm dead but pid file exists"
		fi
	;;

	force-quit)
		echo -n "Terminating php-fpm "

		if [ ! -r $php_fpm_PID ] ; then
			echo "warning, no pid file found - php-fpm is not running ?"
			exit 1
		fi
		pid=$(cat $php_fpm_PID)
		kill -TERM $pid

		wait_for_pid $pid

		echo " done"
	;;

	restart)
		$0 stop
		$0 start
	;;

	reload)

		echo -n "Reload service php-fpm "

		if [ ! -r $php_fpm_PID ] ; then
			echo "warning, no pid file found - php-fpm is not running ?"
			exit 1
		fi
		pid=$(cat $php_fpm_PID)
		error=$($0 start >/dev/null)
		[[ "$error" != "" ]] && echo $error && exit 1

		kill -QUIT $pid
		# 这里等待该pid似乎也不太好
		echo " done"
	;;

	configtest)
		$php_fpm_BIN -t
	;;

	*)
		echo "Usage: $0 {start|stop|force-quit|restart|reload|status|configtest}"
		exit 1
	;;

esac

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#! /bin/sh

### BEGIN INIT INFO

# Provides: php-fpm

# Required-Start: $remote_fs $network

# Required-Stop: $remote_fs $network

# Default-Start: 2 3 4 5

# Default-Stop: 0 1 6

# Short-Description: starts php-fpm

# Description: starts the PHP FastCGI Process Manager daemon

### END INIT INFO

php_fpm_BIN=/usr/sbin/php-fpm

php_fpm_CONF=/etc/php/php-fpm.conf

php_fpm_PID=/var/run/php-fpm.pid

tmp_pid=/var/run/php-fpm.tmp.pid

php_opts="--fpm-config $php_fpm_CONF --pid $tmp_pid"

wait_for_pid () {

local pid=$1

while kill -0 $pid >/dev/null 2>&1 ; do

sleep 1;

done

}

case "$1" in

start)

echo -n "Starting php-fpm "

$php_fpm_BIN --daemonize $php_opts

if [ "$?" != 0 ] ; then

echo " failed"

exit 1

cat $tmp_pid >$php_fpm_PID

echo " done"

;;

stop)

echo -n "Gracefully shutting down php-fpm "

if [ ! -r $php_fpm_PID ] ; then

echo "warning, no pid file found - php-fpm is not running ?"

exit 1

pid=$(cat $php_fpm_PID)

kill -QUIT $pid

wait_for_pid $pid

echo " done"

;;

status)

if [ ! -r $php_fpm_PID ] ; then

echo "php-fpm is stopped"

exit 0

PID=`cat $php_fpm_PID`

if ps -p $PID | grep -q $PID; then

echo "php-fpm (pid $PID) is running..."

else

echo "php-fpm dead but pid file exists"

;;

force-quit)

echo -n "Terminating php-fpm "

if [ ! -r $php_fpm_PID ] ; then

echo "warning, no pid file found - php-fpm is not running ?"

exit 1

pid=$(cat $php_fpm_PID)

kill -TERM $pid

wait_for_pid $pid

echo " done"

;;

restart)

$0 stop

$0 start

;;

reload)

echo -n "Reload service php-fpm "

if [ ! -r $php_fpm_PID ] ; then

echo "warning, no pid file found - php-fpm is not running ?"

exit 1

pid=$(cat $php_fpm_PID)

error=$($0 start >/dev/null)

[[ "$error" != "" ]] && echo $error && exit 1

kill -QUIT $pid

# 这里等待该pid似乎也不太好

echo " done"

;;

configtest)

$php_fpm_BIN -t

;;

echo "Usage: $0 {start|stop|force-quit|restart|reload|status|configtest}"

exit 1

;;

esac

注意：

该功能要求linux内核版本较高，需要支持socket的SO_REUSEPORT 特性，我的3.10的内核已经支持了
php-fpm 的pid文件是php-fpm进程来维护的，同时启动多个php-fpm不太方便，所以需要玩一些手段；虽然不指定pid文件参数也可以，但是我不知道如何才能方便地拿到php-fpm的pid信息，所以还是指定了pid参数

原文链接：https://phpor.net/blog/post/4401

关于PHP中的长连接

PHP No Responses »

2,969

11月 292016

长连接（也叫持久连接）是啥？

对于PHP来讲，如果是运行在web模式，每次请求完成，php会回收所有需要的申请的资源，但是也可以申请一些特殊的资源，php可以不回收，比如：长连接。

优点：长连接省却了每次连接的麻烦，也有效减少了timewait的数量

长连接真的好吗？

PHP中没有提供关闭（销毁）长连接的方法，当长连接出现意外时，将无所适从，更常见的是请求超时，都很不方便处理
同一个服务只能存在一个连接，如果想非阻塞地并发请求同一个服务（相同的目标ip、port），做不到！第二次的pfsockopen得到的是第一次pfsockopen的那个连接，php不会标识一个长连接是否在使用中

鉴于上面两点，感觉长连接真的好鸡肋

原文链接：https://phpor.net/blog/post/4391

PHP5 升级到PHP7时curl注意事项

PHP No Responses »

5,016

11月 092016

（从大量的CLOSE_WAIT发现的问题）

脚本：

<?php
$url = $argv[1];
$mm = array();
function curl($url) {
	global $mm;
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $url);
	#curl_setopt($ch, CURLOPT_HTTPHEADER, array("Connection: close"));
	curl_exec($ch);
	$mm[] = $ch;
	curl_close($ch);
}
for($i = 0; $i < 1000; $i ++) {
	curl($url);
}

<?php

$url = $argv[1];

$mm = array();

function curl($url) {

global $mm;

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, $url);

#curl_setopt($ch, CURLOPT_HTTPHEADER, array("Connection: close"));

curl_exec($ch);

$mm[] = $ch;

curl_close($ch);

}

for($i = 0; $i < 1000; $i ++) {

curl($url);

}

对于curl来说：

如果请求头中含有 Connection: close 则，执行完请求之后，curl会主动关闭连接，即使不主动curl_close() 也没有关系
如果请求头中没有Connection: close，则：
1. 如果curl句柄被销毁了，则连接自动关闭
2. 如果句柄没有被销毁（如：被保存到了全局（或其他静态）变量中），则：
  1. PHP5中，curl_close() 可以关闭连接
  2. PHP7中，curl_close() 不会关闭连接（或许他猜测你可能还会用到），如果你不小心把句柄保存起来了，那么会有什么问题呢? 问题：
    服务器端等待足够长时间后要关闭连接，而客户端却不做任何处理，导致连接处于CLOSE_WAIT状态，如果足够多，会导致local port被用完。
    不过，这个问题看似不好解决，也比PHP5中好处理，PHP5中如果调用了curl_close，而且还把curl句柄保存了起来，则可能会出现保存了大量的句柄而自己却不知道（就是所谓的内存泄漏）

原文链接：https://phpor.net/blog/post/4326

当tinyproxy遇上php的soap

soap No Responses »

5,515

11月 042016

用例：

使用tinyproxy-1.8.3做代理
php访问soap服务时，使用tinyproxy做代理访问http地址（不是https）
http响应数据有点儿多，走的是Transfer-Encoding: chunked

问题：

tinyproxy代理之后，响应头中 HTTP协议版本号为1.1，没有content-length, 也没有connection: close ，也没有Transfer-Encoding: chunked，对于这种尴尬的情况，client端就不方便处理了； curl会有如下警告： no chunk, no close, no size. Assume close to signal end
真实原因： curl虽然使用HTTP/1.1方式发送请求，但是tinyproxy对于所有http请求都以HTTP/1.0的方式转发(但是添加了Connection: close 头)，最终的openresty（nginx行为也如此）却无视HTTP/1.0，执意返回HTTP/1.1 响应，并且使用Connection: close; tinyproxy直接透传HTTP/1.1 状态行，却丢弃了响应头中的Connection: close;(或许是tinyproxy以为自己总是工作在HTTP/1.0，所以不需要Connection: close 吧）

tinyproxy转发的请求：（发给nginx，nginx再代理转发给后面的openresty）

GET / HTTP/1.0
Host: op-phpor.i.hrbbwx.com
Connection: close
Accept: */*
User-Agent: curl/7.29.0

GET / HTTP/1.0

Host: op-phpor.i.hrbbwx.com

Connection: close

Accept: */*

User-Agent: curl/7.29.0

openresty收到的请求：

GET / HTTP/1.0
Host: op-phpor.i.hrbbwx.com
Connection: close
Accept: */*
User-Agent: curl/7.29.0

GET / HTTP/1.0

Host: op-phpor.i.hrbbwx.com

Connection: close

Accept: */*

User-Agent: curl/7.29.0

openresty响应：

HTTP/1.1 200 OK
Server: openresty/1.9.15.1
Date: Sat, 05 Nov 2016 02:51:16 GMT
Content-Type: text/html; charset=UTF-8
Connection: close

HTTP/1.1 200 OK

Server: openresty/1.9.15.1

Date: Sat, 05 Nov 2016 02:51:16 GMT

Content-Type: text/html; charset=UTF-8

Connection: close

openresty是藏在一个nginx后面的，nginx的响应：

HTTP/1.1 200 OK
Server: nginx/1.7.4
Date: Sat, 05 Nov 2016 02:51:16 GMT
Content-Type: text/html; charset=UTF-8
Connection: close

HTTP/1.1 200 OK

Server: nginx/1.7.4

Date: Sat, 05 Nov 2016 02:51:16 GMT

Content-Type: text/html; charset=UTF-8

Connection: close

分析：

原本HTTP/1.0 是不支持Host头的，但是很多client还是添加了，很多server也不介意（甚至喜欢）HTTP/1.0协议中使用Host头，参考： http://stackoverflow.com/questions/246859/http-1-0-vs-1-1

Connection 头也是http1.1中定义的，但是tinyproxy也用在了HTTP/1.0中了（难道为了兼容一些不守规矩的server端？），在HTTP/1.0和Connection头的暗示下，server端没有使用Content-length 或 Transfer-encoding也可以理解，也或许正式Connection头的存在，server端才选择响应HTTP/1.1

tinyproxy 源码片段：

tiny proxy发送请求：

static int
establish_http_connection (struct conn_s *connptr, struct request_s *request)
{
        char portbuff[7];
        char dst[sizeof(struct in6_addr)];

        /* Build a port string if it's not a standard port */
        if (request->port != HTTP_PORT && request->port != HTTP_PORT_SSL)
                snprintf (portbuff, 7, ":%u", request->port);
        else
                portbuff[0] = '\0';

        if (inet_pton(AF_INET6, request->host, dst) > 0) {
                /* host is an IPv6 address literal, so surround it with
                 * [] */
                return write_message (connptr->server_fd,
                                      "%s %s HTTP/1.0\r\n"
                                      "Host: [%s]%s\r\n"
                                      "Connection: close\r\n",
                                      request->method, request->path,
                                      request->host, portbuff);
        } else {
                return write_message (connptr->server_fd,
                                      "%s %s HTTP/1.0\r\n"
                                      "Host: %s%s\r\n"
                                      "Connection: close\r\n",
                                      request->method, request->path,
                                      request->host, portbuff);
        }
}

static int

establish_http_connection (struct conn_s *connptr, struct request_s *request)

{

char portbuff[7];

char dst[sizeof(struct in6_addr)];

/* Build a port string if it's not a standard port */

if (request->port != HTTP_PORT && request->port != HTTP_PORT_SSL)

snprintf (portbuff, 7, ":%u", request->port);

else

portbuff[0] = '\0';

if (inet_pton(AF_INET6, request->host, dst) > 0) {

/* host is an IPv6 address literal, so surround it with

* [] */

return write_message (connptr->server_fd,

"%s %s HTTP/1.0\r\n"

"Host: [%s]%s\r\n"

"Connection: close\r\n",

request->method, request->path,

request->host, portbuff);

} else {

return write_message (connptr->server_fd,

"%s %s HTTP/1.0\r\n"

"Host: %s%s\r\n"

"Connection: close\r\n",

request->method, request->path,

request->host, portbuff);

}

由于tinyproxy上行的是http/1.0 ,所以会故意将请求头中的connection相关信息去掉，代码如下：

这个函数不仅在process_client_headers 中用到，也在 process_server_headers中用到

解决办法：

如果使用隧道代理的方式，tinyproxy就不会做上述多余的处理了，但是， php的soapclient强制写死的逻辑是：如果方式的是https，则使用隧道代理方式，否则，不走隧道代理方式，可是服务提供的就是http，不是https啊！！！！！！
修复tinyproxy的这个问题，修复方案：
换个proxy

疑问：

如果 content-length 不存在与http 1.0，那么http 1.0中的post请求，post数据长度如何表示？（难道也是关闭连接为止？

原文链接：https://phpor.net/blog/post/4296

java cpu 100% 无响应

Java No Responses »

5,766

10月 132016

占用cpu高的线程的堆栈如下：

Thread 1 (process 17775):
#0  0x00007fa870981179 in Klass::subklass() const () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#1  0x00007fa8706d15c5 in Dependencies::find_finalizable_subclass(Klass*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#2  0x00007fa8705df8ee in ciInstanceKlass::has_finalizable_subclass() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#3  0x00007fa87052483e in GraphBuilder::call_register_finalizer() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#4  0x00007fa87052b2a5 in GraphBuilder::method_return(Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#5  0x00007fa87053185f in GraphBuilder::iterate_bytecodes_for_block(int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#6  0x00007fa87052ec4b in GraphBuilder::iterate_all_blocks(bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#7  0x00007fa87052f5e6 in GraphBuilder::try_inline_full(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#8  0x00007fa87052f7df in GraphBuilder::try_inline(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#9  0x00007fa870530912 in GraphBuilder::invoke(Bytecodes::Code) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#10 0x00007fa87053183d in GraphBuilder::iterate_bytecodes_for_block(int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#11 0x00007fa87052ec4b in GraphBuilder::iterate_all_blocks(bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#12 0x00007fa87052f5e6 in GraphBuilder::try_inline_full(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#13 0x00007fa87052f7df in GraphBuilder::try_inline(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#14 0x00007fa870530912 in GraphBuilder::invoke(Bytecodes::Code) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#15 0x00007fa87053183d in GraphBuilder::iterate_bytecodes_for_block(int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#16 0x00007fa87052ebf2 in GraphBuilder::iterate_all_blocks(bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#17 0x00007fa8705337a7 in GraphBuilder::GraphBuilder(Compilation*, IRScope*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#18 0x00007fa87053c127 in IRScope::IRScope(Compilation*, IRScope*, int, ciMethod*, int, bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#19 0x00007fa87053c23f in IR::IR(Compilation*, ciMethod*, int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#20 0x00007fa87051b25b in Compilation::build_hir() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#21 0x00007fa87051b61e in Compilation::compile_java_method() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#22 0x00007fa87051b74e in Compilation::compile_method() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#23 0x00007fa87051babe in Compilation::Compilation(AbstractCompiler*, ciEnv*, ciMethod*, int, BufferBlob*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#24 0x00007fa87051c869 in Compiler::compile_method(ciEnv*, ciMethod*, int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#25 0x00007fa87066f43a in CompileBroker::invoke_compiler_on_method(CompileTask*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#26 0x00007fa8706703e6 in CompileBroker::compiler_thread_loop() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#27 0x00007fa870c2386f in JavaThread::thread_main_inner() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#28 0x00007fa870c2399c in JavaThread::run() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#29 0x00007fa870ad7de8 in java_start(Thread*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so
#30 0x0000003202c079d1 in start_thread () from /lib64/libpthread.so.0
#31 0x00000032028e88fd in clone () from /lib64/libc.so.6

Thread 1 (process 17775):

#0 0x00007fa870981179 in Klass::subklass() const () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#1 0x00007fa8706d15c5 in Dependencies::find_finalizable_subclass(Klass*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#2 0x00007fa8705df8ee in ciInstanceKlass::has_finalizable_subclass() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#3 0x00007fa87052483e in GraphBuilder::call_register_finalizer() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#4 0x00007fa87052b2a5 in GraphBuilder::method_return(Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#5 0x00007fa87053185f in GraphBuilder::iterate_bytecodes_for_block(int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#6 0x00007fa87052ec4b in GraphBuilder::iterate_all_blocks(bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#7 0x00007fa87052f5e6 in GraphBuilder::try_inline_full(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#8 0x00007fa87052f7df in GraphBuilder::try_inline(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#9 0x00007fa870530912 in GraphBuilder::invoke(Bytecodes::Code) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#10 0x00007fa87053183d in GraphBuilder::iterate_bytecodes_for_block(int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#11 0x00007fa87052ec4b in GraphBuilder::iterate_all_blocks(bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#12 0x00007fa87052f5e6 in GraphBuilder::try_inline_full(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#13 0x00007fa87052f7df in GraphBuilder::try_inline(ciMethod*, bool, Bytecodes::Code, Instruction*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#14 0x00007fa870530912 in GraphBuilder::invoke(Bytecodes::Code) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#15 0x00007fa87053183d in GraphBuilder::iterate_bytecodes_for_block(int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#16 0x00007fa87052ebf2 in GraphBuilder::iterate_all_blocks(bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#17 0x00007fa8705337a7 in GraphBuilder::GraphBuilder(Compilation*, IRScope*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#18 0x00007fa87053c127 in IRScope::IRScope(Compilation*, IRScope*, int, ciMethod*, int, bool) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#19 0x00007fa87053c23f in IR::IR(Compilation*, ciMethod*, int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#20 0x00007fa87051b25b in Compilation::build_hir() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#21 0x00007fa87051b61e in Compilation::compile_java_method() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#22 0x00007fa87051b74e in Compilation::compile_method() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#23 0x00007fa87051babe in Compilation::Compilation(AbstractCompiler*, ciEnv*, ciMethod*, int, BufferBlob*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#24 0x00007fa87051c869 in Compiler::compile_method(ciEnv*, ciMethod*, int) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#25 0x00007fa87066f43a in CompileBroker::invoke_compiler_on_method(CompileTask*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#26 0x00007fa8706703e6 in CompileBroker::compiler_thread_loop() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#27 0x00007fa870c2386f in JavaThread::thread_main_inner() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#28 0x00007fa870c2399c in JavaThread::run() () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#29 0x00007fa870ad7de8 in java_start(Thread*) () from /usr/java/jdk1.8.0_45/jre/lib/amd64/server/libjvm.so

#30 0x0000003202c079d1 in start_thread () from /lib64/libpthread.so.0

#31 0x00000032028e88fd in clone () from /lib64/libc.so.6

gdb 跟进发现：线程在函数Dependencies::find_finalizable_subclass(Klass*) 中，应该有一个循环，不断地调用函数Klass::subklass()

解决办法：

The fix was simple – disable CMS class unloading options when -Xnoclassgc or -XX:-ClassUnloading are specified.

参考资料：

https://blogs.oracle.com/poonam/entry/jvm_hang_with_cms_collector

想阅读jvm源码吗？ https://blogs.oracle.com/sundararajan/entry/so_you_want_to_read

原文链接：https://phpor.net/blog/post/4194

JVM监控与调优

Java No Responses »

2,237

10月 102016

http://www.cnblogs.com/zhguang/p/Java-JVM-GC.html

查看默认的最大堆设置：

java  -XshowSettings:vm

1	java -XshowSettings:vm

原文链接：https://phpor.net/blog/post/4156

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