RFR: 8153334: Replace BufferedInputStreams use of AtomicReferenceFieldUpdater with Unsafe

[Remi Forax]

----- Mail original -----
> De: "Paul Sandoz" <paul.sandoz at oracle.com>
> Cc: "core-libs-dev Libs" <core-libs-dev at openjdk.java.net>
> Envoyé: Mercredi 6 Avril 2016 16:09:14
> Objet: Re: RFR: 8153334: Replace BufferedInputStreams use of	AtomicReferenceFieldUpdater with Unsafe
> 
> 
> > On 6 Apr 2016, at 15:28, forax at univ-mlv.fr wrote:
> > 
> > > > While i fully agree in the general case, in disagree for this specific
> > > > case,
> > > > there are few uses of ARFU inside the JDK (or outside) but currently
> > > > because BufferedInputStream uses an ARFU, each time someone starts a
> > > > Java
> > > > application, the VM loads ARFU and its implementation with a high
> > > > probability to no need it at all after
> > > >
> > >
> > > Does that really contribute sufficiently to slow down in start time? It
> > > really seems like a micro-optimisation.
> > 
> > small streams become big rivers (i don't know the idiomatic sentence in
> > English, so it's a rough translation from a French idiom),
> > "Death by a thousand cuts" is one of my favorites :).  A "flat profile" is
> > another description of a similar thing.
> > 
> I still remain unconvinced in this case that such changes warrant an increase
> in unsafe usage (temporary or otherwise).

Ok, you win :)

> 
> > In general, I agree that easy/cheap/maintainable/etc wins should be done
> > even if individually they don't matter much (if that were the requirement,
> > there would be no progress whatsoever).
> > 
> > In this case, using Unsafe for now seems trivial; when VH is ready, someone
> > is going to sweep the code anyway and this will be just one more place to
> > mechanically update.  Is VH definitely going to be part of Java 9? If so,
> > then perhaps no point in making this change unless it's going to be
> > backported to Java 8.
> > 
> > Also don't forget that releasing VarHandle API as a public API for 9 is
> > vastly different from replacing all usages of Unsafe by some VarHandle
> > methods inside the JDK, see Paul's answser about the bootstrap issues.
> > 
> 
> VHs are now in jdk9/dev. I dunno when it will rise up to the master and the
> next EA build.

Oh, i didn't notice.
congrat !

> 
> Paul.
> 

Rémi