On Tue, May 24, 2011 at 13:47, Andrew Haley <aph@xxxxxxxxxx> wrote: > Ever since > Compressed OOPs became the default there's no big advantage to running > 32-bit Java, at least on HotSpot. ---- What are the performance characteristics of 64-bit versus 32-bit VMs? Generally, the benefits of being able to address larger amounts of memory come with a small performance loss in 64-bit VMs versus running the same application on a 32-bit VM. This is due to the fact that every native pointer in the system takes up 8 bytes instead of 4. The loading of this extra data has an impact on memory usage which translates to slightly slower execution depending on how many pointers get loaded during the execution of your Java program. The good news is that with AMD64 and EM64T platforms running in 64-bit mode, the Java VM gets some additional registers which it can use to generate more efficient native instruction sequences. These extra registers increase performance to the point where there is often no performance loss at all when comparing 32 to 64-bit execution speed. The performance difference comparing an application running on a 64-bit platform versus a 32-bit platform on SPARC is on the order of 10-20% degradation when you move to a 64-bit VM. On AMD64 and EM64T platforms this difference ranges from 0-15% depending on the amount of pointer accessing your application performs. ---- http://www.oracle.com/technetwork/java/hotspotfaq-138619.html#64bit_performance "0 to 15% performance degradation" does not equal "thereÂs no big advantage" (to run 32-bit JVMs). FC -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
