Hi, The following webrev http://cr.openjdk.java.net/~enevill/8149365/webrev.0/ adds support for prefetch on backwards copies (previously prefetch was only done on forwards copies). It also fixes a 'feature' where the command line option -XX:PrefetchCopyIntervalInBytes=N is ignored and the value 256 always used instead. I have benchmarked it using the following test progam http://cr.openjdk.java.net/~enevill/8149365/ArrayCopyTest.java Which allows you to test memory copies of different sizes from a start size to an end size in step units. The test does both backwards and forwards copies. Usage: java ArrayCopyTest <iters> <start> <end> <step> I have generated the results obtained before and after the above patch on 4 different partners HW (A,B,C,D) and a summary of the results is available at http://people.linaro.org/~edward.nevill/prefetch/prefetch.pdf For partner A I tested 3 ranges 0-64 bytes in units of 1 0-512 bytes in units of 8 0-4096 bytes in units of 64 The latter 2 clearly show the benefit of prefetching on backwards copies. For partners B, C & D, I only tested 0-4096 bytes in units of 64. I also tested B, C & D with -XX:PrefetchCopyIntervalInBytes=0. On these 3 partners disabling prefetch seemed to have no effect indicating that either prefetch is not implemented, or it implements automatic hardware prefetch. A summary of the results is that it improves performance significantly on partner A and has no effect on partners B,C & D. OK to push? Ed.