On 03/08/2016 04:06 PM, Paul Sandoz wrote: > Please pre-emptively review a fix to update the buffer implementations to > leverage the Unsafe unaligned accessors: > > > http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8151163-buffer-unsafe-unaligned-access/webrev/
*) My concern with using double-register Unsafe calls is that compilers are unable to speculate on (hb == null) value, which means you will have the additional field read on the fast path. See: https://bugs.openjdk.java.net/browse/JDK-8150921 http://cr.openjdk.java.net/~shade/8150921/notes.txt So, while I agree that using double-register unaligned accessors are cleaner, I'd try to special-case (bb.hb == null) case for Heap* buffers. Current patch might still be better than going through Bits though. > The changes in this webrev take advantage of those for JDK-8149469 > and apply the unsafe double addressing scheme so certain byte buffer > view implementations can work across heap and direct buffers. This > should improve the performance on x86 for: I understand the idea, but I think we would need to verify this before pushing. Thanks, -Aleksey
