Official support for Unsafe

[Quân Anh Mai]

Hi,

The issue with the maintainability of jdk.internal.misc.Unsafe is that it
is too powerful. I imagine getIntUnchecked(int[], int) can be implemented
in Java as a simple index access, and C2 will parse it similar to a index
operation apart from the bound check.

Please correct me if I do not comprehend the complexity of this matter.
Thanks a lot,
Quan Anh

On Sat, 13 Jan 2024 at 02:40, Remi Forax <forax at univ-mlv.fr> wrote:

> Hello mery kitty,
> ""Safety"" is half of the problem here.
>
> The other half is the cost of maintaining an official API to do native
> access and the fact that it will make future features/optimizations harder
> or impossible (cf the work to support sun.misc.Unsafe in Valhalla).
>
> We already provide command line options to access to
> jdk.internal.misc.Unsafe (--add-exports/-add-opens) that are already too
> powerful IMO, but at least the contract is clear, any classes in
> jdk.internal.blah may change in the next JDK.
>
> So you can access to the extra 1% if you want, at the cost of having to
> track the changes of the internal classes of the JDK. That is a fair deal
> for me.
>
> regards,
> Rémi
>
> ------------------------------
>
> *From: *"Brian Goetz" <brian.goetz at oracle.com>
> *To: *"Maurizio Cimadamore" <maurizio.cimadamore at oracle.com>
> *Cc: *"Quân Anh Mai" <anhmdq at gmail.com>, "amber-dev" <
> amber-dev at openjdk.org>
> *Sent: *Friday, January 12, 2024 6:00:58 PM
> *Subject: *Re: Official support for Unsafe
>
> Indeed, this is the whole question: how much of *everyone’s* safety are we
> willing to trade to make the already-pretty-good, 99.999% case run a little
> faster.
>
> On Jan 12, 2024, at 11:52 AM, Maurizio Cimadamore <
> maurizio.cimadamore at oracle.com> wrote:
>
> Heck, looking at the results of the 1brc competition, your pure Java
> solution (no Unsafe, just FFM) ended up scoring quite high (3rd!) - at some
> point the question has to become: how much safety I'm willing to sacrifice
> to get an extra 1% ? I know that's a subjective decision, of course, but
> it's one that, as a community, we need to gripple with (as that has deep
> repercussions on the rest of the ecosystem).
>
>
>
>
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