Thread Test on HotSpot 1.7

JVM Tutorials - Herong's Tutorial Examples

∟Thread Test on HotSpot 1.7

This section provides a tutorial example to see how many running threads can be supported on HotSpot 1.7.0_45 Client and Server JVMs.

This test of CrashThread.java is done with HotSpot Client JVM 1.7.0 on my Windows 7 system.

herong> \Progra~1\java\jdk1.7.0_45\bin\javac CrashThread2.java

herong> \Progra~1\java\jdk1.7.0_45\bin\java -Xmx2m CrashThread2 64

Time   Threads   T.Memory   F.Memory
8:07:32 PM   1   1984   1563
8:07:32 PM   2   1984   1563
8:07:32 PM   3   1984   1563
...
8:07:32 PM   62   1984   1509
8:07:32 PM   63   1984   1509
8:07:32 PM   64   1984   1509

There is no problem for HotSpot Client JVM to support for 64 running threads. However, when I look at the Task Manager, I noticed that the JVM is taking 99% of CPU time and 7,348K of memory. And my computer becomes slow.

Then I increased # of threads to higher values, I observed the following on system Task Manager:

HotSpot Client JVM 1.7.0_45
Threads   CPU    Memory   System
     64   99%    7,348K   slow
    128   99%    9,488K   slow
    256   99%   13,696K   slow
    512   99%   22,392K   very slow
   1024   99%   39,700K   very slow
   2048   99%   73,256K   extremely slow

I repeated the same test on HotSpot Server JVM 1.7.0_45 and observed similar results:

HotSpot Server JVM 1.7.0_45
Threads   CPU    Memory   System
     64   99%    8,712K   slow
    128   99%   10,800K   slow
    256   99%   14,988K   slow
    512   99%   23,700K   very slow
   1024   99%   40,992K   very slow
   2048   99%   75,333K   extremely slow