Fwd: RFR 8151163 All Buffer implementations should leverage Unsafe unaligned accessors

[Paul Sandoz]

I forgot include nio-dev…

Email thread is here:

  http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-March/thread.html#39364 <http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-March/thread.html#39364>

Paul.

> Begin forwarded message:
> 
> From: Paul Sandoz <paul.sandoz at oracle.com>
> Subject: RFR 8151163 All Buffer implementations should leverage Unsafe unaligned accessors
> Date: 8 March 2016 14:06:37 CET
> To: core-libs-dev <core-libs-dev at openjdk.java.net>, hotspot-dev developers <hotspot-dev at openjdk.java.net>
> 
> Hi,
> 
> 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/
> 
>  http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8151163-buffer-unsafe-unaligned-access-hotspot/webrev/
> 
> The JDK changes depend on those for the following which is in CCC review:
> 
>  https://bugs.openjdk.java.net/browse/JDK-8149469
>  ByteBuffer API and implementation enhancements for VarHandles
> 
>  http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8149469-byte-buffer-align-and-unifying-enhancements/webrev/
> 
> 
> 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:
> 
> 1) direct ByteBuffers using the wider unit size method accessors; and
> 2) wider unit size views over heap ByteBuffers.
> 
> As a consequence Bits.java has greatly reduced in size :-)
> 
> 
> The HotSpot changes update the test that was originally added when the heap ByteBuffer method accessors were updated to utilise unsafe unaligned access. I split the test out so as to reduce the execution time, since I doubled the amount of tests. These tests could be improved for views at various unaligned/unaligned positions in the byte buffer, but i left that for now.
> 
> I plan to push through hs-comp since JDK-8149469 will go through hs-comp.
> 
> Later on today i will kick of a JPRT hotspot test run.
> 
> —
> 
> This is a small step towards unifying the buffer implementations using the unsafe double addressing scheme:
> 
>  https://bugs.openjdk.java.net/browse/JDK-6509032
> 
> Thanks,
> Paul.

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