> V8 still uses STW for mark sweep. Well unfortunately you are still misunderstanding, so let me be more precise so we are talking about the same thing. V8 use

> V8 still uses STW for mark sweep. Well unfortunately you are still misunderstanding, so let me be more precise so we are talking about the same thing. V8 uses incremental marking (i.e. splitting mark work into smaller chunks and interleaving those chunks with mutator time) as well as concurrent marking (i.e. multiple parallel collector threads marking in the background, concurrent with the mutator). Not mentioned in the article, but sweeping of pages is also incremental (i.e. dead space reclaimed on-demand when free lists run empty) and concurrent when idle (i.e. in the background). So the statement "V8 still uses STW for mark sweep" is just wrong. Like I said before, V8 only stops the world for semispace scavenges (fast, < 1ms) and compaction (slow, ??ms), but compaction is less frequent than mark/sweep, which is incremental and concurrent. You also misunderstood what is reported here. That 50ms main thread marking time is cumulative, meaning those 50ms are spread over the entire garbage collection cycle, split up into small increments so that the mutator (main thread) is not stopped the entire time. It's explained there in the text and illustrated in the second-to-last diagram. > quite bad compared to ~5ms or less Again, it is not 50ms pause, it's 50ms work, split into much, much smaller incremental pauses, typically less than 1 ms each. That number is not presented in your linked article but is pretty typical. The V8 GC needs sub-millisecond pause times because it has a soft realtime requirement in that it may end up on the critical path for frame rendering (60fps = 16.6ms). > For Go, I'm going to be a bad HN user and not read the whole article. FTA "...The August 2017 release saw little improvement. We know what is causing the remaining pauses. The SLO whisper number here is around 100-200 microseconds and we will push towards that. If you see anything over a couple hundred microseconds then we really want to talk to you and figure out whether it fits into the stuff we know about or whether it is something new we haven't looked into. In any case there seems to be little call for lower latency. It is important to note these latency levels can happen for a wide variety of non-GC reasons..." TLDR: if you see pause times of more than a couple hundred microseconds, call the red phone. Also, please note, I am just trying to provide accurate information about the collectors I do know about, designed by people I work(ed) with. I don't know enough about ZGC or Shenenadoah to confidently assert anything about their performance characteristics, but based on what I read I am actually very excited to see them make it into production. I consider advances in GC to be overall a good thing for everyone, and would encourage you to be more open to learning the advantages and disadvantages of various systems without as much derision and not try to pick sides.