ブロックしない fwrite（のはずが全然速くならなかった）

non-blocking-fwrite.php

<?php
$str = str_repeat(PHP_VERSION, 200000);
$len = strlen($str);
$r = null;
$e = null;
$w = [];
$bytes = [];

foreach (range(1, 100) as $i) {
    $w[] = $fp = fopen("test{$i}.txt", 'wb');
    $bytes[(string)$fp] = $len;
    stream_set_blocking($fp, false);
}

while (false !== $result = stream_select($r, $w, $e, 50)) {
    foreach ($w as $i => $fp) {
        $written = $bytes[(string)$fp] -= fwrite($fp, $str);
        if ($written <= 0) {
            unset($w[$i]);
        }
    }
    if (!$w) {
        break;
    }
}