Java multicore and multithreading

2010-10-10  来源:本站原创  分类:Java  人气:147 

Recently been discussed in the forum to see multi-core, then,

Associated with multi-core and multithreading so what's it?

I did an experiment,
Implementation environment:
AMD Athlon (tm) 64 X2 Dual Core
Ubuntu i386 / kernel: linux 2.6.32-25

1.Main function in the time to start a thread, a CPU 100%

2.Main function in the start when the two threads, 2 CPU 100%

3.Main function in a thread, but start 2 times, and the effect of two similar

Conclusion: The system will automatically deploy CPU, and found that the system will automatically use two CPU utilization in the smaller CPU.
That is, multi-core CPU running multi-threaded program, if the program does not specify when the CPU information, OS CPU core will be responsible for scheduling and management of multi-core CPU does not need to consider OS scheduling. But if they want to balance the load of multi-core CPU, when you create the thread, you can specify the thread's CPU affinity (CPU Affinity), using as linux c api: sched_setaffinity, windows c api: SetProcessAffinityMask, SetThreadAffinityMask function, can interfere with OS of thread scheduling, balance CPU load.


In the core cpu running on the specified thread (c / c + +):

JAVA so it?

In the JRockit JVM Management API you can at least Suggest the Process affinity. Not sure if IT is respected on the OS you're running. See manapi / Docs / COM / bea / JVM / JVM.html # suggestProcessAffinity (java.util.Collection) for more Information.

JVM jvm = JVMFactory.getJVM ();
List cpus = new ArrayList ();
for (Iterator it = JVMFactory.getJVM (). getProcessAffinity (). iterator (); it.hasNext ();)
CPU cpu = (CPU) ();
jvm.suggestProcessAffinity (cpus);

You can find JRockit here.

I used taskset on my 4 cpu machine, and by using:
taskset-pc 0 java net.tilialacus.BusyThreads
I gbound all threads to cpu 0. (BusyThreads just runs a few threads with
while (true);

However, if I started the process first, then I have to bind all threads
manually to the CPU. Using ps-eLf I could list all threads (10 or so)
and I could bind each of them separately. I didn't find a way for
taskset to climb the process / thread tree automatically.

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