(PHP 5)
proc_nice — Change the priority of the current process
$increment
)
proc_nice() changes the priority of the current
process by the amount specified in increment. A
positive increment will lower the priority of the
current process, whereas a negative increment
will raise the priority.
proc_nice() is not related to proc_open() and its associated functions in any way.
increment
The increment value of the priority change.
成功时返回 TRUE， 或者在失败时返回 FALSE。
If an error occurs, like the user lacks permission to change the priority,
an error of level E_WARNING is also generated.
Note: Availability
proc_nice() will only exist if your system has 'nice' capabilities. 'nice' conforms to: SVr4, SVID EXT, AT&T, X/OPEN, BSD 4.3. This means that proc_nice() is not available on Windows.
kevin AT REMOVETHIS mrkmg.com (2013-04-19 18:17:38)
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 );
?>
Marek (2011-01-19 08:40:43)
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.
php at richardneill dot org (2010-06-24 00:14:34)
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"
pandi at home dot pl (2008-11-25 05:22:11)
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]) ? $matches[2] : null));
}
?>
php at riggers dot me dot uk (2004-08-12 16:20:37)
Just an addition to the previous note re: exec('renice...'). The exit_func() will not set the priority back to normal (0) (at least on linux), unless the user that the webserver is running as is a super user (bad idea). You can decrease the priority of the running task, but not increase it again. See man page for renice.
To prevent subsequent requests running at the lower priority I called apache_child_terminate() on shutdown.
griph at dd dot chalmer dot se (2003-11-10 14:34:52)
If you don't have PHP5 and needs to nice your process this works good.
<?php
function proc_nice($priority) {
exec("renice +$priority ".getmypid());
}
//You also need a shutdown function if you don't want to leave your http deamons with a modified priority
function exit_func(){
// Restore priority
proc_nice(0);
}
register_shutdown_function('exit_func');
?>