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Editorial Team
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Asked: 2026-06-01T03:15:32+00:00

I am just trying to avoid context switching as it introduces a lot of

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I am just trying to avoid context switching as it introduces a lot of latency. So If I am thinking that correctly, I want to have at maximum one thread per processor. If the processor supports virtual parallelism (hyper-threading I think it is the name!) then I can have the double number of threads.

Ex: 4 processors with hyperthreading = 8 threads max.

Of course the OS needs the processor as well, so I am maybe being naive here.

Anyways, knowing the number of threads the JVM creates on startup is a good start.

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1 Answer

  1. Editorial Team

    The JVM only starts 1 user thread, also called the “Main” thread. There are other threads that are running behind the scenes such as garbage collectors, compilers, optimizers, finalizers, etc..

    A quick look at a thread dump for a nothing little app:

    public static void main(String[] args) throws Exception {
    Thread.sleep(100000);
}

    Shows:

    "Low Memory Detector" daemon prio=5 tid=7f810c801000]
"C2 CompilerThread1" daemon prio=9 tid=7f810c800000
"C2 CompilerThread0" daemon prio=9 tid=7f8107037000
"Signal Dispatcher" daemon prio=9 tid=7f8107036000
"Surrogate Locker Thread (Concurrent GC)" daemon prio=5 tid=7f8107801000 
"Finalizer" daemon prio=8 tid=7f810882a000 nid=0x1118cb000 
"Reference Handler" daemon prio=10 tid=7f8108829000 nid=0x1117c8000 
"main" prio=5 tid=7f8104801000 nid=0x109a52000 waiting on condition
"VM Thread" prio=9 tid=7f8108824800 nid=0x1116c5000 runnable 
"Gang worker#0 (Parallel GC Threads)" prio=9 tid=7f8104802800
"Gang worker#1 (Parallel GC Threads)" prio=9 tid=7f8104803000 
"Gang worker#2 (Parallel GC Threads)" prio=9 tid=7f8104803800 
"Gang worker#3 (Parallel GC Threads)" prio=9 tid=7f8107800000 
"Gang worker#4 (Parallel GC Threads)" prio=9 tid=7f8108800000 
"Gang worker#5 (Parallel GC Threads)" prio=9 tid=7f8107000800
"Gang worker#6 (Parallel GC Threads)" prio=9 tid=7f8107001000
"Gang worker#7 (Parallel GC Threads)" prio=9 tid=7f8107002000 
"Concurrent Mark-Sweep GC Thread" prio=9 tid=7f810701c000
"Gang worker#0 (Parallel CMS Threads)" prio=9 tid=7f81090c3000
"Gang worker#1 (Parallel CMS Threads)" prio=9 tid=7f810701b800
"VM Periodic Task Thread" prio=10 tid=7f810c812800 
"Exception Catcher Thread" prio=10 tid=7f8104801800
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