CODEWITHSUNDEEP
phpcpu-usage
matteo
matteo

Reputation: 3067

How can I get the real CPU time used in PHP?

How can I calculate the CPU time actually used by my php script?

Note this is NOT what I'm looking for:

<?php
$begin_time=microtime(true);
//..
//end of the script:
$total_time=microtime(true)-$begin_time;

because that would give me the time elapsed. That may include a lot of time used by unrelated processes running at the same time, as well as time spent waiting for i/o.

I've seen there is getrusage(), but a user comment in the documentation page says:

getrusage() reports kernel counters that are updated only once application loses context and a switch to kernel space happens. For example on modern Linux server kernels that would mean that getrusage() calls would return information rounded at 10ms, desktop kernels - at 1ms.

getrusage() isn't usable for micro-measurements at all - and getmicrotime(true) might be much more valuable resource.

so that doesn't seem to be an option, is it?

What alternatives do I have?

Upvotes: 4

Views: 4326

Answers (2)

SnakeMaster
SnakeMaster

Reputation: 97

You can use getrusage()

Full example:

<?php

function rutime($ru, $rus, $index){
    return ($ru["ru_$index.tv_sec"]*1000 + intval($ru["ru_$index.tv_usec"]/1000))
     -  ($rus["ru_$index.tv_sec"]*1000 + intval($rus["ru_$index.tv_usec"]/1000));
}

$cpu_before = getrusage();
$ms = microtime(true) * 1000;

sleep(3);
$tab = [];
for($i = 0; $i < 500000; $i++) {
  $tab[] = $i;
}

$cpu_after = getrusage();
echo "Took ".rutime($cpu_after, $cpu_before, "utime")." ms CPU usage" . PHP_EOL;
echo "Took ".((microtime(true) * 1000) - $ms)." ms total". PHP_EOL;

Source: https://helpdesk.nodehost.ca/en/article/how-to-calculate-real-cpu-usage-in-a-php-script-o3ceu8/

Upvotes: 0

Zak
Zak

Reputation: 25205

Define "your" I/O. Technically a move of memory to cpu registers is I/O. Are you saying you want to remove that time from your calculation? (I'm guessing no)

What I'm getting at is you are looking to profile your code in some way most likely. If you want to measure time not spent reading/writing to files or network sockets, just use microtime and put extra calls around portions doing I/O. Then you will also get an idea of how much time your I/O is taking. More likely you will find you have some loop taking more time than you expect.

When I profile like this I either use profiling tools in eclipse, or I use a time logger and do some kind of binary search-ish insertion of the time logging into the code. Usually I find some small area of code that is taking 85% of the measured time and do optimization there.

Also as a side note, don't let the perfect become the enemy of the practical. 90% of the time during your process your calls won't be interrupted by some other process and your microtime counts will be close enough.

Upvotes: 1

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