use of Unsafe for ASCII detection
aleksey.shipilev at oracle.com
Tue Jan 12 20:49:29 UTC 2016
On 01/07/2016 02:21 AM, Martin Buchholz wrote:
> A stupid benchmark (sorry Aleksey - maybe you already have a jmh
> version of this?) http://cr.openjdk.java.net/~martin/Utf8Bench.java
Okay, I'll bite:
As Andrew already pointed out, the trick is to get the ByteBuffer byte
order to native, and use JDK 9 with getLongUnaligned bells and whistles.
As Paul suggested, VarHandles views could be used to always avoid
ByteBuffer allocation, even though compilers are moderately successful
in removing them.
> It's hard to resist Unsafe when it gives 3x improvement in a
> performance hotspot. Maybe C2 can optimize the simple loop even more
> than it is today?
It would seem that with JDK 9, you don't need Unsafe in this scenario.
ByteBuffers provide a comparable performance, and VarHandles would push
the envelope a bit further, since we are implicitly optimizing the
internal APIs to boost them up.
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