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

[Tristan Tarrant]

Hi Sanne,

ultimately I believe that it is not about the "intrinsic" (sorry for 
overloading the term) performance of the memory allocation invocations, 
but the advantage of using ByteBuffers as the de-facto standard for 
passing data around between Infinispan, JGroups and any I/O layers 
(network, disk). Removing various points of copying, marshalling, etc is 
the real win.

Tristan

On 01/20/2014 03:01 PM, Sanne Grinovero wrote:
> 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
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