Huge performance impact from 3.8.0 to 3.9.0

[j0r1s]

Hi everyone,

I have a CMS Symfony project using agence-adeliom/easy-editor-bundle, and over the years, the number of blocks has grown quite substantially.

Each block can be added to the page content using its prototype. However, after upgrading twig/twig from 3.8.0 to 3.9.0, I've noticed massive increases in rendering times for admin pages:

Before Upgrade:

After Upgrade:

While I understand that dumping every prototype into the DOM might not be the most efficient implementation, I'm puzzled by the significant performance drop from a minor version upgrade.

I've seen changes about the escaper in the changelog, which might be a lead.
I've narrowed down the rendering time hit to this line in the editor_widget.html.twig template:

data-prototype='{{ form_row(prototypes[type])|e('html_attr') }}'

This line is called once for every block type (49 times in my current example), and if I remove it, the rendering time improves drastically.

I would greatly appreciate any help or insights on how to tackle this issue since I prefer not to lock my Twig version to 3.8.0.

Thank you in advance for your assistance!

[fabpot]

"I'm puzzled by the significant performance drop from a minor version upgrade" You make it sound like we're fine with such a performance drop (and maybe that we were aware of it), which we're not obviously. This should be considered a bug that needs to be fixed if possible. To help with our investigation, could you try to write a reproducer that we can then profile with Blackfire to better understand the bottleneck?

[j0r1s]

I didn't mean to imply that you were okay with such a performance drop; I just didn't want to come across as rude.

Thank you for taking the time to respond!

I've created a public repository that illustrates the issue, and I've included instructions in the README.

Please let me know if there's anything else I can do to help.

[xabbuh]

I have profiled your application. Here are the results:

• with Twig 3.8: https://blackfire.io/profiles/9404b76f-c246-4b7a-ac67-a804dd268f1e/graph
• with Twig 3.10:https://blackfire.io/profiles/dcc4ecb5-91f7-4bc6-a5a0-72bc4e668fed/graph
• comparison: https://blackfire.io/profiles/compare/a287033c-ab80-4bcf-a179-861b93272555/graph

[fabpot]

AFAIU, the problem is the captureOutput() method that is needed for BC.

[j0r1s]

Thanks for your analysis.

Is there then anything I can do in order to avoid locking my project's twig version to 3.8 ?

[nicolas-grekas]

If I enable the "use_yield" mode, the page rendering goes from 22s to 3s on my machine.
The issue is that there is no easy way to enable this mode in Symfony 6.4. Maybe we should consider having one?
Another idea might be to generate "echo" instead of "yield" when not in yield mode (right now we always use "yield" and we "echo" them when not in yield mode)

(I'd also recommend to improve the easy-editor-bundle. The number of iterations looks unreasonable to me for the result on this page.)

[shyim]

Yes, it would be nice if there would be a flag in Symfony 6.4/7.0/7.1.

Twig 3.8:

[nix-shell:~/Developer/sw-trunk]$ hyperfine --warmup 3 'php custom/scripts/twig.php'
Benchmark 1: php custom/scripts/twig.php
  Time (mean ± σ):     220.1 ms ±   2.0 ms    [User: 164.7 ms, System: 46.5 ms]
  Range (min … max):   217.6 ms … 224.6 ms    13 runs

Without yield:

Benchmark 1: php custom/scripts/twig.php
  Time (mean ± σ):     258.0 ms ±   2.1 ms    [User: 201.9 ms, System: 47.1 ms]
  Range (min … max):   253.9 ms … 261.4 ms    11 runs

With yield:

[nix-shell:~/Developer/sw-trunk]$ hyperfine --warmup 3 'php custom/scripts/twig.php'
Benchmark 1: php custom/scripts/twig.php
  Time (mean ± σ):     222.9 ms ±   2.0 ms    [User: 167.5 ms, System: 46.7 ms]
  Range (min … max):   220.1 ms … 227.1 ms    13 runs

[smnandre]

Is there a way to add one on Symfony 6.4 ? Any idea how to handle this ?

[smnandre]

Found this the other day... is the comment still valid today (the xdebug part) ?

    public function renderBlock(FormView $view, mixed $resource, string $blockName, array $variables = []): string
    {
        $cacheKey = $view->vars[self::CACHE_KEY_VAR];

        $context = $this->environment->mergeGlobals($variables);

        ob_start();

        // By contract,This method can only be called after getting the resource
        // (which is passed to the method). Getting a resource for the first time
        // (with an empty cache) is guaranteed to invoke loadResourcesFromTheme(),
        // where the property $template is initialized.

        // We do not call renderBlock here to avoid too many nested level calls
        // (XDebug limits the level to 100 by default)
        $this->template->displayBlock($blockName, $context, $this->resources[$cacheKey]);

        return ob_get_clean();
    }

I don't have all the history of this method.. but i kinda (maybe naively) feel that either renderBlock or yieldBlock could really ease things here, no ?

[fabpot]

Fixed by #4216