(PECL eio >= 0.0.1dev)
eio_busy — Artificially increase load. Could be useful in tests, benchmarking
$delay,$pri = EIO_PRI_DEFAULT,$callback = NULL,$data = NULL
eio_busy() artificially increases load taking
delay seconds to execute. May be used for debugging,
or benchmarking.
delayDelay in seconds
pri请求的优先级：EIO_PRI_DEFAULT，EIO_PRI_MIN，EIO_PRI_MAX 或 null。如果是
null，pri 将设为
EIO_PRI_DEFAULT。
callbackThis callback is called when all the group requests are done.
data
Arbitrary variable passed to callback.
eio_busy() returns request resource on success, 或者在失败时返回 false.