How to make script execution delay < 10 milliseconds?

Question

PHP

There is a loop, inside the usleep() function pauses the execution of each iteration for a given number of microseconds (millionths of a second). I want the script to pause for 10 milliseconds (i.e. 10 thousandths of a second). Looks like this:

for($i = 1; $i <= 1000; $i ++){
    /*
    * какой-то код
    */
    usleep(10000); //это 0,010 секунды
}

The problem is that a delay of 10 and less than 10 milliseconds does not work, at least 20 milliseconds. Here's what they write about on the topic :
Delays of less than 50 milliseconds (depending on the speed of the processor, machine, and system load) are not possible, because. it takes at least 10-30 milliseconds to return control to a process in Linux. Specifying such delays for usleep(3) will actually result in a longer delay (at least 10ms).
Question: Is it possible to reduce the delay in usleep() to less than 10 milliseconds? What about time_nanosleep(), where a delay of 1 billionth of a second is possible? The server is on FreeBSD 9.1

Answer 1

$lastTime = microtime(true);

for($i = 1; $i <= 1000; $i ++){
    while (true)
    {
           $new_last = microtime(true);
           if ($new_last - $lastTime > 0.010)
           {
                    $lastTime = $new_last;
                    break;
           }
    }

    /*
    * какой-то код
    */
}

Answer 2

I became curious, php went to remember
this code from me:

var_dump(number_format(microtime(true), 6));
time_nanosleep(0, 10 * 1000 * 1000);
echo "<br />";
var_dump(number_format(microtime(true), 6));

output the following:

string(20) "1,396,895,032.113305" 
string(20) "1,396,895,032.123673"

time_nanosleep - put everything to sleep for 10 milliseconds

Answer 3

How then is time_nanosleep() where a delay of 1 billionth of a second is possible

Who told you? You can specify the desired time with an accuracy of 1ns, but what the actual delay will be depends on very, very many factors.