I have some scripts that use a ton of cpu is it possible to cap the amount of cpu a process is allowed to use? I am running on CentOs 5.5 by the way.
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Do you mean in the php code itself? You may be able to limit the php scripting engine through the OS but that wouldn't be programming relatedYWE– YWE2010-09-26 03:04:05 +00:00Commented Sep 26, 2010 at 3:04
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3 Answers
I helped a fellow PHP coder create PHP scripts which address a similar issue. These are long-running PHP scripts which generate a lot of load. Since they're long running, the goal was to "pause" them if load gets too high. The script has a function similar to:
function get_server_load()
{
$fh = fopen('/proc/loadavg', 'r')
$data = fread($fh, 6);
fclose($fh);
$load_avg = explode(" ", $data);
return floatval(trim($load_avg[0]));
}
The script calls get_server_load() during each loop, and if the load is greater than a given max, it sleeps for 30 seconds and checks again:
set_time_limit(120);
while(get_server_load() > $max_load)
sleep($load_sleep_time);
This allows the script to give CPU time back to the server during periods of high load.
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Krunoslav Djakovic
This is nice approach, but note that you are returning int, not float, so you can't get load average of 0.9 eg.
PHP is considered a scripting language, and does not have such low level access to the hardware.
Instead, what you can do is use functions like "set_time_limit()"
http://php.net/manual/en/function.set-time-limit.php
and memory_limit in your php.ini
http://php.net/manual/en/ini.core.php
Those are the recommended methods, but the closest you'll get to what you want are probably a combination of "sleep()"
http://php.net/manual/en/function.sleep.php
and getting the current CPU load with "exec('uptime');". Note that you may or may not have access to those system commands.
