Performance regression in PHP 8.3

[andypost]

Description

The following code:

<?php

$post_max_size = 8 * 1024 * 1024;

function generateFile($filename, $width, $lines, $type = 'binary-text') {
  $text = '';
  $t0 = microtime(TRUE);

  for ($i = 0; $i < $lines; $i++) {
    // Generate $width - 1 characters to leave space for the "\n" character.
    for ($j = 0; $j < $width - 1; $j++) {
      switch ($type) {
        case 'text':
          $text .= chr(rand(32, 126));
          break;

        case 'binary':
          $text .= chr(rand(0, 31));
          break;

        case 'binary-text':
        default:
          $text .= rand(0, 1);
          break;
      }
    }
    $text .= "\n";
    $t1 = microtime(TRUE);
    print "Iteration $i - " . (($t1 - $t0) * 1000) . ' ms' . "\n";
    $t0 = $t1;
  }

  // Create filename.
  $filename = '/tmp/' . $filename . '.txt';
  //file_put_contents($filename, $text);
  return $filename;
}

echo generateFile('exceeding_post_max_size', ceil(($post_max_size + 1024) / 1024), 1024);

Resulted in this output in previous versions:

...
Iteration 1016 - 1.060962677002 ms
Iteration 1017 - 1.3351440429688 ms
Iteration 1018 - 1.4958381652832 ms
Iteration 1019 - 1.5652179718018 ms
Iteration 1020 - 1.133918762207 ms
Iteration 1021 - 1.3449192047119 ms
Iteration 1022 - 1.0910034179688 ms
Iteration 1023 - 2.5720596313477 ms

But I'm getting this output instead:

Iteration 0 - 1.6670227050781 ms
Iteration 1 - 3.5400390625 ms
Iteration 2 - 5.9168338775635 ms
Iteration 3 - 8.7440013885498 ms
Iteration 4 - 11.125087738037 ms
Iteration 5 - 13.100862503052 ms
Iteration 6 - 14.358997344971 ms
Iteration 7 - 19.643068313599 ms
Iteration 8 - 21.284103393555 ms
Iteration 9 - 24.443864822388 ms
Iteration 10 - 29.021978378296 ms
Iteration 11 - 29.219150543213 ms
Iteration 12 - 29.844999313354 ms
Iteration 13 - 33.437013626099 ms
Iteration 14 - 35.980939865112 ms
Iteration 15 - 37.060976028442 ms
Iteration 16 - 40.301084518433 ms
Iteration 17 - 45.086860656738 ms
Iteration 18 - 47.156095504761 ms
Iteration 19 - 54.861068725586 ms
Iteration 20 - 59.279918670654 ms
Iteration 21 - 55.058002471924 ms
Iteration 22 - 62.628984451294 ms
Iteration 23 - 62.710046768188 ms
Iteration 24 - 66.666841506958 ms
Iteration 25 - 67.9612159729 ms
Iteration 26 - 73.35090637207 ms
Iteration 27 - 73.814868927002 ms
Iteration 28 - 81.268072128296 ms
Iteration 29 - 86.863994598389 ms
Iteration 30 - 86.045980453491 ms
Iteration 31 - 89.563131332397 ms
Iteration 32 - 93.811988830566 ms
Iteration 33 - 104.84790802002 ms
Iteration 34 - 103.92713546753 ms
Iteration 35 - 118.44992637634 ms
Iteration 36 - 117.29502677917 ms
Iteration 37 - 122.51305580139 ms
Iteration 38 - 147.05491065979 ms
Iteration 39 - 145.72691917419 ms
Iteration 40 - 145.61200141907 ms
Iteration 41 - 157.13310241699 ms
Iteration 42 - 132.14802742004 ms
Iteration 43 - 134.90295410156 ms
Iteration 44 - 139.23907279968 ms
Iteration 45 - 172.71780967712 ms
Iteration 46 - 156.75115585327 ms
Iteration 47 - 142.99201965332 ms
Iteration 48 - 142.3168182373 ms
Iteration 49 - 142.22002029419 ms
Iteration 50 - 147.85099029541 ms
Iteration 51 - 150.74706077576 ms
Iteration 52 - 183.83002281189 ms
Iteration 53 - 185.53805351257 ms
Iteration 54 - 156.80599212646 ms
Iteration 55 - 165.35997390747 ms
Iteration 56 - 180.59802055359 ms
Iteration 57 - 179.68106269836 ms
Iteration 58 - 180.39298057556 ms
Iteration 59 - 176.19895935059 ms

PHP Version

PHP 8.3.0-alpha2

Operating System

Alpinelinux, Ubuntu

[andypost]

https://3v4l.org/WciJK shows that previously it was a constant time

It makes 1 test of Drupal to hang forever with following strace

• https://www.drupal.org/project/drupal/issues/3366843#comment-15116535
• https://www.drupal.org/files/issues/2023-06-22/php83a2-strace-drupal11.png

[iluuu1994]

This seems to be due to 727e26f. @nielsdos I can investigate, if you aren't already.

[nielsdos]

I was about to post a PR. It's actually bcuz of 7790ee8

[iluuu1994]

@nielsdos Ah I see, that's my bad, thank you!