[JFR incubator] [RFR] JDK-8238590: Enable JFR by default during compilation in 8u

[Ben Evans]

On Mon, Feb 17, 2020 at 7:10 PM Andrew John Hughes <gnu.andrew at redhat.com>
wrote:

>
>
> On 14/02/2020 17:39, Mario Torre wrote:
> > Il giorno ven 14 feb 2020 alle ore 18:16 Andrew John Hughes
> > <gnu.andrew at redhat.com> ha scritto:
> >
> >> As to enabling by default, I would suggest that we delay this until the
> >> October cycle, so we have one cycle with the code present, but manually
> >> enabled, and then spend the 8u272 cycle explicitly testing the effects
> >> of default enablement. I think having it on by default is the right
> >> path, but there's no need to rush it.
> >
> > Yes, I agree and this was my original idea, but during the Committers
> > workshop was specifically asked to enable it by default right away.
> > Nonetheless, I don't mind either way :)
> >
> > I can skip this change if so agreed.
> >
>
> I'm not suggesting to skip it. I'm suggesting it should happen after the
> release of 8u262, so there is a release with the code integrated, but
> disabled by default.
>
> I see no rush into turning it on for everyone by default.
>

 I completely agree. I have anecdotal reports of performance regression
with the JFR code compiled in, but those are against the incubator repo so
it's not apples-apples.

Having the JFR code in mainline, disabled by default but capable of manual
enablement will greatly simplify the process of getting properly accurate
feedback - and will hopefully mean broader testing from a wider range of
users as well.

I'm very, very keen to get JFR available for everyone using JDK 8, but in
my opinion a few months delay is greatly preferable to the risk of a
performance regression that could affect people's ability to upgrade to
8u262+

Thanks,

Ben