最近在論壇裏看到有人討論多核，那麼，
多核和多線程有啥關聯呢？
我做了個實驗，
實現環境：
AMD Athlon(tm) 64 X2 Dual Core
Ubuntu i386/內核: linux 2.6.32-25
OpenJDK6
1.Main函數裏啓動一個線程時候， 一個CPU 100%
2.Main函數裏啓動兩個線程的時候，2個CPU 100%
3.Main 函數裏1個線程，但同時啓動2次，和效果2類似
結論：系統會自動調配CPU，而且發現系統會自動使用 2個CPU中利用率較小的CPU。
即，多核CPU運行多線程程序，如果編程時候沒有指定CPU信息，OS會負責CPU內核的調度和管理，不需要考慮OS的多核CPU調度的。但是如果自己想
均衡多核CPU的負載，在創建線程的時候，可以指定線程的CPU親和性(CPU Affinity),使用如 linux c api:sched_setaffinity，windows c api:SetProcessAffinityMask、SetThreadAffinityMask函數，可以實現干預OS對線程的調度，均衡CPU負載。
附：
在指定cpu的核心上執行線程（c/c++）: http://www.cppblog.com/Khan/archive/2009/12/29/104384.html
那麼JAVA呢？
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 http://e-docs.bea.com/jrockit/releases/R27/javadoc/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) it.next();
jvm.suggestProcessAffinity(cpus);
}
You can find JRockit here.
http://www.oracle.com/technology/software/products/jrockit/index.html
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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.