Steps to reproduce the issue

applications that are using joomla's cache handler:

$cache = JFactory::getCache('my_key','callback');
$cache->setCaching(true);
$cache->call( array( 'MyClass', 'MyFunction' ),$param1,$param2,$param3);

the cache handlers in joomla do usleep on a first round even when the key hasn't yet been created within the cache handlers.

related joomla core files with usleep:
\libraries\joomla\cache\storage\file.php
\libraries\joomla\cache\cache.php

• other handlers

original code in file.php
[code]
usleep(100);
$data_lock = @flock($_fileopen, LOCK_EX);
[/code]
suggested code (to usleep only after the first round):
[code]
$data_lock = @flock($_fileopen, LOCK_EX);
if ($data_lock === false) {
usleep(100);
}
[/code]

since locking is handled in the handler (file and others) i do not see the point to delay script with usleep in the main cache class:
\libraries\joomla\cache\cache.php

Expected result

adding Nx 2x 100 microsends to the page load depending on N number of times of calling the cache function while having an empty cache.

Actual result

slow site, lower SEO

System information (as much as possible)

php 5.5 on joomla 3.5.1

Additional comments