251. Tackling G1 latency improvements
G1 GC latency has also recorded some improvements from JDK 8 to JDK 20 (which are obviously reflected in G1 GC throughput as well).
In order to decrease latency, G1 has passed through several changes, as follows.
Merge parallel phases into a larger one
Starting with JDK 8, many aspects of G1 have been parallelized. In other words, at any moment in time, we may have in execution multiple parallel phases. Starting with JDK 9, these parallel phases can be merged into a single larger one. In practice, this means less synchronization and less time spent creating/destroying threads. As a result, this improvement speeds up the parallelization processing, leading to less latency.
Reduction of metadata
Reduction of metadata was added in JDK 11. Practically, G1 attempts to manage less metadata by reducing its amount as much as possible. Less data to manage means better latency. Of course, this means a smaller footprint as well.
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