[infinispan-dev] Performance of accessing off-heap buffers: NIO & Unsafe

[Sanne Grinovero]

At our meeting last week, there was a debate about the fact that the
(various) off-heap buffer usage proposals, including NIO2 reads, would
potentially be slower because of it potentially needing more "native"
invocations.

At the following link you can see the full list of methods which will
actually be optimised using "intrinsics" i.e. being replaced by the
compiler as it was a macro with highly optimized ad-hoc code which
might be platform dependant (or in other words, which will be able to
take best advantage of the capabilities of the executing platform):

http://hg.openjdk.java.net/jdk8/awt/hotspot/file/d61761bf3050/src/share/vm/classfile/vmSymbols.hpp

In particular, note the "do_intrinsic" qualifier marking all uses of
Unsafe and the NIO Buffer.

Hope you'll all agree now that further arguing about any of this will
be dismissed unless we want to talk about measurements :-)

Kudos to all scepticals (always good), still let's not dismiss the
large work needed for this yet, nor let us revert from the rightful
path until we know we've tried it to the end: I do not expect to see
incremental performance improvements while we make progress, it might
even slow down until we get to the larger rewards.

Cheers,
Sanne