ackfoobar 10 hours ago

Probably yes.

https://bugs.openjdk.org/browse/JDK-8076103

Closed with "Won't Fix".

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lbalazscs 11 hours ago

In 2015 there was no ZGC. Today ZGC (an optional garbage collector optimized for latency) guarantees that there will be no GC pauses longer than a millisecond.

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  • survivedurcode 10 hours ago

    I would check your answer. These are pauses due to time spent writing to diagnostic outputs. These are not traditional collection pauses. This affects both jstat as well as writes of GC logs. (I.e. GC log writes will block the app just the same way)

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    • pjmlp 10 hours ago

      Which is why for anything serious one should be using Flight Recorder instead.

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  • esaym 7 hours ago

    These modern garbage collectors are not simply free though. I got bored last year and went on a deep dive with GC params for Minecraft. For my needs I ended up with: -XX:+UseParallelGC -XX:MaxGCPauseMillis=300 -Xmx2G -Xms768M

    When flying around in spectator mode, you'd see 3 to 4 processes using 100%. Changing to more modern collectors just added more load to the system. ZGC was the worst, with 16+ processes all using 100% cpu. With the ParallelGC, yes you'll get the occasional pause but at least my laptop is not burning hot fire.

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    • plandis 6 hours ago

      Yes no GC is free (well perhaps Epsilon comes close :)

      It’s a low pause GC so latencies, particularly tail latencies, can be more predictable and bounded. The tradeoff you make is that it uses more CPU time and memory in order to operate.

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    • namibj 7 hours ago

      You'll need more spare heap for ZGC.

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      • ackfoobar 6 hours ago

        And using generational ZGC will probably lower CPU usage a lot.

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  • kanzenryu2 7 hours ago

    Sadly in many cases no; it's not magic. This nirvana is restricted to cases where there is CPU bandwidth available (e.g. some cores idle) and plenty of free RAM. When either CPU or RAM are less plentiful... hello pauses my old friend.

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    • sunshowers 7 hours ago

      This is why memory-bound services generally use languages without mandatory GC. Tail latency is a killer.

      Rust's memory management does have some issues in practice (large synchronous drops) but they're relatively minor and easily addressed compared to mandatory GC.

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  • hawk_ 10 hours ago

    ZGC doesn't remove safepoint requests on threads which is the root cause. "Guarantees" here are with very heavy quotes.

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  • hinkley 7 hours ago

    The cost of statistics gathering on a GC implementation that avoids ineffective GC activity is less affected by the cost of telemetry (no news is good news), but it is still affected.

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