Why latency increases when a "while loop" PHP script is called several times?

Asked Jun 18 '16 at 13:23

Active Jun 18 '16 at 13:29

Viewed 120 times

This pair of scripts shows what I mean:

client (JS)

$.ping = function(i_max) {
    $.get('ping.php', {
        'i_max': i_max,
        'client_start': Date.now() / 1000
    }).done(function(d){
        console.log(d);
    })
}

server (PHP)

$client_start = $_GET['client_start'];
$server_start = round(microtime(true) * 1000) / 1000;
$diff = $server_start - $client_start;
$i = 0;
$i_max = $_GET['i_max'];
while($i < $i_max) {
    sleep(1);
    $i++;
}
echo "i_max = $i_max => diff = $diff\n";

When few instances are run latency is good, beyond, latency goes bad, is there an option to set in php.ini? Here is a console screenshot:

edited Jun 18 '16 at 13:29

asked Jun 18 '16 at 13:23

ubugnu

1,004
2
15
30

what are you're trying to achieve? – strangeqargo Jun 18 '16 at 13:32
What are you using as your webserver? It may only be handling one request at a time, so your `$.ping(0)` must wait until the `$.ping(10)` calls have finished first. – slugonamission Jun 18 '16 at 13:32
@strangeqargo concurrent requests that wait for a data to be available on the server in a while loop – ubugnu Jun 18 '16 at 13:35
Chrome can't be a web server. Where is your PHP code? – slugonamission Jun 18 '16 at 13:37
@slugonamission sorry, apache2 – ubugnu Jun 18 '16 at 13:38
I'm not blaming the browser, I'm blaming your web server. Anyway, potentially have a look at http://stackoverflow.com/questions/1430883/simultaneous-requests-to-php-script for more information. – slugonamission Jun 18 '16 at 13:39
how many threads are "more than a few"? – strangeqargo Jun 18 '16 at 13:47
@strangeqargo on my localhost, above 2, on an amazon server, more than 5 – ubugnu Jun 18 '16 at 13:48
seems it's bound to cpu cores, you should try to test your script with nginx or change apache's mpm module (https://www.digitalocean.com/community/tutorials/apache-vs-nginx-practical-considerations) – strangeqargo Jun 18 '16 at 13:57

Why latency increases when a "while loop" PHP script is called several times?

0 Answers0