[upstream] Fetching normalizers seems slow

I've already linked it there. Based on a gut feeling this seems the same - we aim at reducing normalizer look-ups.

Yeah but Drupal has something like 30+ normalizers registered in the container. So getNormalizer loops 14k times * 30 => 300-400k supports normalization calls out of the blue... Symphony one is not a bad system, we just need to put the most important one first, so we spare the excessive looping.

As we essentially out-scoped this form the other issue and opened a core to resolve this directly, should this be closed?

As it was found in the other issue(s) there is a performance fix upstream in symphony (4.1).

This is the tuned version of the hack from the other issue that resolved a BIG portion of the overhead from Symfony/Component/Serializer/Serializer::getNormalizer(...) class.

# ...
    private $normalizersCache = [];

    /**
     * Returns a matching normalizer.
     *
     * @param mixed  $data    Data to get the serializer for
     * @param string $format  Format name, present to give the option to normalizers to act differently based on formats
     * @param array  $context Options available to the normalizer
     *
     * @return NormalizerInterface|null
     */
    private function getNormalizer($data, $format, array $context)
    {
        $type = \is_object($data) ? \get_class($data) : 'native-' . \gettype($data);
        $cacheId = "normalizer:$type:$format";
        if (isset($this->normalizersCache[$cacheId]) || array_key_exists($cacheId, $this->normalizersCache)) {
          return $this->normalizersCache[$cacheId];
        }

        foreach ($this->normalizers as $normalizer) {
            if ($normalizer instanceof NormalizerInterface && $normalizer->supportsNormalization($data, $format, $context)) {
                return $this->normalizersCache[$cacheId] = $normalizer;
            }
        }

        return $this->normalizersCache[$cacheId] = null;
    }
# ...

Responses from jsonapi are exactly the same.

Here is before...

and after...

... the code above was applied.

I plan to have a patch posted here for that library.
Even if not recommended, this is speeding-up the ::getNormalizer() method with close to a second of run-time for my case or about 30+ times.

Here is the promised patch...
I am not putting into needs review as it's for my own use (unless anyone likes it) :D

@Renrhaf thanks for the feedback.
You should consider the latest version of jsonapi or paching the one in 8.7 with #2819335: Resource (entity) normalization should use partial caching.

Adding the core issue that caused this, as a related one.
Updated issue summary with note about the PoC patch in #8.

And another that will work for symfony/serializer:3.4.37.