I don't want to spam original issue regarding testing results of this PR. I've just retested this with the zip I attached in issue, I can confirm promising results: getting 4s with a patch and ~49s without this patch.

I've also retested my normal project from which I extracted the demo, there time didn't change much (which makes sense, I already replaced injections of these problematic services with container injections there). This time I used your link to 4.4 file, perhaps during my previous testing I applied patch in this PR manually wrong and that resulted in some infinite loop.

Thank you @ostrolucky for your tests.

This PR changes a lot of things in the way the container is Dumped, The output of the circularReferences before and after the PR are not comparable but the dumped container is identical in the cases I tested.

I think we should test this PR is several different configuration to be sure.

Rework a little bit the implementation with the help of @nicolas-grekas

Now reduced by 88% CPU time for the same memory usage https://blackfire.io/profiles/compare/ba4c464a-4449-4633-99a8-fcf31bcc948c/graph

Thank you @jderusse.

Just a heads up, I've built the Symfony containers for https://github.com/kocsismate/php-di-container-benchmarks via PHP 8, running on Docker on my laptop:

• v5.1.8: 11805.0532 ms
• 5.x-dev: 14068.2973 ms

I ran the container building script multiple times, but the results stayed consistent (within +-1 sec).

Hello @kocsismate , thanks for reporting these numbers.

You compared 2 differents version of the component (5.1 vs 5.2).
Could you please compare with version v5.2.0-BETA3

From my side I tried with PHP 7.4, and got ~similar numbers.
5.2.0-BETA3: 1928.255282 ms
5.2-dev: 1995.516162 ms

Note, I also extract number from the part that have been optimized (dumping the php code)

diff --git a/src/Container/Symfony/SymfonyContainerAdapter.php b/src/Container/Symfony/SymfonyContainerAdapter.php
index 4f7d174..69f4921 100644
--- a/src/Container/Symfony/SymfonyContainerAdapter.php
+++ b/src/Container/Symfony/SymfonyContainerAdapter.php
@@ -139,6 +139,8 @@ final class SymfonyContainerAdapter implements ContainerAdapterInterface
     protected function dumpContainer(ContainerBuilder $containerBuilder, string $path, string $class, bool $asFiles): void
     {
         $dumper = new PhpDumper($containerBuilder);
+
+        $s = microtime(true);
         $content = $dumper->dump(
             [
                 "namespace" => "DiContainerBenchmarks\\Container\\Symfony\\Resource",
@@ -147,6 +149,7 @@ final class SymfonyContainerAdapter implements ContainerAdapterInterface
                 "debug" => false,
             ]
         );
+        var_dump(microtime(true) - $s);
 
         if ($asFiles) {
             $file = key($content);

and get very similar number:
5.2.0-BETA3: float(0.035419940948486) => 354 ms
5.2-dev: float(0.037868022918701) => 378 ms

The result are ~ identical because your project does not have many circular references, thus you were not impacted by the bug.

Yeah, I can confirm, 5.2.0-BETA3 and 5.2-dev yields nearly the same results. Thanks for the explanation about the difference between my initial two measurements!