[11u] RFR: 8257602: Introduce JFR Event Throttling and new jdk.ObjectAllocationSample event (enabled by default)

[Langer, Christoph]

Hi Jaroslav,

I think this is a great enhancement for JFR - but as the word "enhancement" says, it's not a bugfix. So it's not a "must have" for a backport to the LTS. With enhancements we need first of all be very cautious not to endanger stability.

I suggest you get in touch with Red Hat's team around Mario Torre to discuss the idea and feasibility of backporting this to 11u. I think it really has to be discussed whether this item is a good candidate for a backport at all and if so, what testing and other precautions need to be taken before letting this in.

So, for the moment I'll flag the bug with a jdk11u-fix-no. But feel invited to re-request approval via removing that flag after more discussion has been done and a consensus is reached in the community.

Thanks for your understanding!

Best regards
Christoph


> -----Original Message-----
> From: jdk-updates-dev <jdk-updates-dev-retn at openjdk.java.net> On
> Behalf Of Jaroslav Bachorík
> Sent: Montag, 21. Dezember 2020 16:23
> To: jdk-updates-dev <jdk-updates-dev at openjdk.java.net>
> Subject: Re: [11u] RFR: 8257602: Introduce JFR Event Throttling and new
> jdk.ObjectAllocationSample event (enabled by default)
> 
> Greetings,
> 
> The original attempt to generate webrev from two changesets failed
> miserably. Therefore I am updating the webrev links as follows:
> * Main issue:
> http://cr.openjdk.java.net/~jbachorik/8257602/jdk11/00/webrev/
> * Followup AIX build fix:
> https://cr.openjdk.java.net/~jbachorik/8258094/jdk11/00/webrev/
> 
> Regards,
> 
> -JB-
> 
> On Tue, Dec 15, 2020 at 9:21 AM Jaroslav Bachorík
> <jaroslav.bachorik at datadoghq.com> wrote:
> >
> > Greetings,
> >
> > I would like to ask for review of this JDK11u backport patch:
> >
> > Issue   :  https://bugs.openjdk.java.net/browse/JDK-8257602
> > Webrev:
> http://cr.openjdk.java.net/~jbachorik/8257602/jdk11/00/webrev/
> >
> > The webrev contains the main change backported from JDK-8257602 and
> > the followup patch for AIX build failure resolved as JDK-8258094. I
> > decided to roll both changesets into one webrev to get a fully
> > buildable system once this backport request is approved.
> >
> > The original changeset of JDK-8257602 had to be slightly adjusted for
> > the following:
> > * hunk offsets not matching because of larger structural changes
> >    resolution: the appropriate code was inserted manually
> > * missing Atomic::load_acquire and Atomic::release_store functions
> >    resolution: used OrderAccess::* equivalents
> > * different argument order for Atomic::cmpxchg and Atomic::store
> >    resolution: modified the call-site argument order to match what is
> > provided by Atomic::*
> > * [test] missing support for event streaming
> >    resolution: used the recording in non-streaming mode while keeping
> > the test semantics
> >
> > All tier1, tier2 and jdk_jfr tests are passing with the changes applied.
> >
> > Cheers,
> >
> > -JB-