This function is particularly necessary on VMs running on KVM, XEN (openstack, AWS EC2, etc) when timing execution times.
On these platforms which lack vDSO the common method of using time() or microtime() can dramatically increase CPU/execution time due to the context switching from userland to kernel when running the `gettimeofday()` system call.
The common pattern is:
<?php
$time = -microtime(true);
sleep(5);
$end = sprintf('%f', $time += microtime(true));
?>
Substituted as:
<?php
$start=hrtime(true);
sleep(5);
$end=hrtime(true);
$eta=$end-$start;
echo $eta/1e+6; //nanoseconds to milliseconds
//5000.362419
//OR simply
$eta=-hrtime(true);
sleep(5);
$eta+=hrtime(true);
echo $eta/1e+6; //nanoseconds to milliseconds
//5000.088229
?>
There is also the new StopWatch class http://php.net/manual/en/class.hrtime-stopwatch.php
hrtime
(PHP 7 >= 7.3.0, PHP 8)
hrtime — Get the system's high resolution time
Description
Returns the system's high resolution time, counted from an arbitrary point in time. The delivered timestamp is monotonic and can not be adjusted.
Return Values
Returns an array of integers in the form [seconds, nanoseconds], if the
parameter as_number is false. Otherwise the nanoseconds
are returned as int (64bit platforms) or float
(32bit platforms).
Returns false on failure.
Examples
Example #1 hrtime() usage
<?php
echo hrtime(true), PHP_EOL;
print_r(hrtime());
?>The above example will output something similar to:
10444739687370679
Array
(
[0] => 10444739
[1] => 687464812
)
See Also
- The High resolution timing extension
- microtime() - Return current Unix timestamp with microseconds
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User Contributed Notes 1 note
SenseiSimple ¶
6 years ago
