prefetch instructions in Hotspot

[Vladimir Kozlov]

Code looks fine. But you should know that such software prefetches only help when you access memory without patterns 
otherwise hardware prefetches in modern cpus will give you much better results. You also need to prefetch far a head of 
load instructions.

Regards,
Vladimir

On 4/4/14 4:24 AM, Mahmood Naderan wrote:
> OK guys. Thanks to Vladimir and others I added the declarations and compiled JDK6 successfully. Then based on the test example provided here (http://hg.openjdk.java.net/jdk6/jdk6/hotspot/file/d98807bff770/test/compiler/6968348/Test6968348.java) I wrote the following code to see if I am using the prefetchRead correctly.
>
> import sun.misc.Unsafe;
> import java.lang.reflect.*;
> public class Arr {
>    static int [] a = new int[3];
>    static Unsafe unsafe;
>    static int baseOffset, indexScale;
>    public static void main(String[] args)  throws Exception {
>      a[0] = 10;
>      a[1] = 20;
>      a[2] = 30;
>
>      Class c = Arr.class.getClassLoader().loadClass("sun.misc.Unsafe");
>      Field f = c.getDeclaredField("theUnsafe");
>      f.setAccessible(true);
>      unsafe = (Unsafe)f.get(c);
>
>      baseOffset = unsafe.arrayBaseOffset(int[].class);
>      indexScale = unsafe.arrayIndexScale(int[].class);
>      for (int i = 0; i < 3; i++)  {
>        unsafe.prefetchReadStatic(a, baseOffset+indexScale*i);
>        System.out.println(a[i]);
>      }
>    }
> }
>
>
>
> Running the code shows everything is fine and the values are printed on the screen.
> Just need a confirmation; is that a correct usage of prefetchRead()? Is that all?
>
>
> Regards,
> Mahmood
>
>
>
>
>
> On Thursday, April 3, 2014 6:36 PM, "dalibor.topic at oracle.com" <dalibor.topic at oracle.com> wrote:
>
>> See top level file Readme-build.html for instructions.
>>
>
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