A way to stop GC wasting CPU time on long-lived objects (GC generations or something else)

Description

PHP's GC is currently unsuited to long-running applications because of the lack of GC generations.

Any application which has long-lived objects with many descendents (such as PocketMine-MP's Server) will currently experience significant performance hits from GC runs due to the expense of repeatedly scanning complex dependencies of these objects.

I haven't dived deep into this problem, but I did verify that just the Server alone winding up in the GC root buffer in PocketMine-MP (which it should never do, being an object that stays alive for almost the entire process) costs 1.7 ms of GC time on a 12700k. An average GC run in PM during normal operation costs somewhere in the ballpark of 15ms, despite creating almost zero cycles.

This is a massive performance impact to PM on account of its update cycle taking place every 50 ms, so a 15ms GC pause is serious business.

Runtimes like .NET and Java have GC generations to avoid this problem, which avoid frequently scanning complex long-lived objects.

I understand that the benefit to PHP is relatively small, given that the primary use case is to serve short-lived web requests, but implementing generations in GC would positively affect performance of long-lived applications.

先从链接的 PocketMine-MP src/Server.php 示例开始，以了解长生命周期对象图和报告中的 GC 成本。然后定位 PHP 的 GC 实现及相关测试，复现此处描述的重复扫描，并将完成定义为：一种经过测试的方法，能够减少对长生命周期对象的工作量，同时保留循环收集。