On a Linux system, running apache2 as a non-privileged user you can not increase the niceness of the process after decreasing it. Also, you can not use the apache_child_ terminate either. I found the following does work though:
<?php
//decrease niceness
proc_nice(19);
//kill child process to "reset" niceness
posix_kill( getmypid(), 28 );
?>
proc_nice
(PHP 5, PHP 7, PHP 8)
proc_nice — 修改当前进程的优先级
说明
proc_nice() 修改当前进程的优先级，
修改量由 priority 参数指定。
priority 为正数会降低当前进程优先级，
反之，为负数会提高优先级。
proc_nice() 和 proc_open() 函数以及和 proc_open() 相关的函数并无什么关系。
参数
-
priority -
新的优先级值，具体的设定取决于所运行的平台。
在 Unix 系统上，较小的值表示较高的优先级，例如：
-20， 而正数值表示更低的优先级。在 Windows 平台上，
priority参数 的含义如下：优先级 可能的值 高优先级 priority< -9较高优先级 priority< -4正常优先级 priority< 5&priority> -5较低优先级 priority> 5低优先级 priority> 9
返回值
成功时返回 true， 或者在失败时返回 false。。
如果发生错误，例如用户无权修改当前进程的优先级，
会生成 E_WARNING 级别的错误。
更新日志
| 版本 | 说明 |
|---|---|
| 7.2.0 | 在 Windows 平台上可用。 |
注释
注意: 可用性
仅在具有 'nice' 能力的系统上才可以使用 proc_nice() 函数。 下列系统含有 'nice'：SVr4, SVID EXT, AT&T, X/OPEN, BSD 4.3。
注意: Windows 平台
proc_nice() 函数会改变当前进程优先级，即使 PHP 是使用线程安全模式编译的。
参见
- pcntl_setpriority() - 修改任意进程的优先级
add a note
User Contributed Notes 5 notes
kevin AT REMOVETHIS mrkmg.com ¶
11 years ago
php at richardneill dot org ¶
14 years ago
If a process is reniced, then all its children inherit that niceness. So a PHP script can call proc_nice on itself, then invoke system(), and the command executed via system() will also be niced.
Also worth making a note of ionice. There's no PHP function for this, but it's important. A nice'd program will happily try to chew up all i/o bandwidth with very little CPU usage, it can therefore make the entire computer non-responsive despite the programmer's intention. Use "ionice -c3" or see "man ionice"
Marek ¶
13 years ago
Regarding ionice - on linux the impact of the ionice -c3 class is similar to that of nice, because the CPU "niceness" is taken into account when calculating the io niceness.
phil_php at zieaon dot com ¶
3 years ago
It is important to note that this is a relative change. I didn't read the description properly and couldn't figure out why setting proc_nice(0) didn't take the forked children back to 0!
For example if you run:
<?php
proc_nice(-5);
proc_nice(0); // will have no effect
proc_nice(5); // will take the niceness back to 0
?>
In PHP CLI under Debian (and probably many other Linux flavours) you can read the 'niceness' from the proc filesystem. (There may be a PHP command that gives this info but there doesn't seem to be a link to it on this page.)
E.g
<?php
$Current_Niceness_Value = intval(explode(" ",file_get_contents("/proc/".getmypid()."/stat"))[18]);
// Note: Older versions of Linux return an unsigned integer which has to be converted to a signed integer.
$Current_Niceness_Value = unpack("l",pack("L",intval(explode(" ",file_get_contents("/proc/".getmypid()."/stat"))[18])))[1];
?>
pandi at home dot pl ¶
16 years ago
Simple function for check process nice, by default returns nice of current process:
<?php
public static function getProcessNice ($pid = null) {
if (!$pid) {
$pid = getmypid ();
}
$res = `ps -p $pid -o "%p %n"`;
preg_match ('/^\s*\w+\s+\w+\s*(\d+)\s+(\d+)/m', $res, $matches);
return array ('pid' => (isset ($matches[1]) ? $matches[1] : null), 'nice' => (isset ($matches[2]) ? $matches[2] : null));
}
?>
