RFR(S) : 8225554 : add JFR event for uncommon trap

[Igor Ignatyev]

Hi Markus,

I definitely support the idea of making the event as helpful for end-users as possible; and having information about the uncommon trap "location" (method, line-number, bci) seems to be very useful. I don't think that 'instruction' field is helpful though b/c w/o seeing the rest of method code it can't be really used to understand what/why happened. what do you think?

regarding the name, although I don't think this even can be used by people w/o understanding some level of hotspot internals, they at least need to understand what a bit cryptic reasons and actions mean, "Deoptimization" sounds good to me.

please let me know how you can proceed further here, I can update my patch to rename even and include location info, or I can just withdraw my patch in favor of yours (that's if you plan to finish work on it in near future and it won't be left for other few years :) ) 

Thanks,
-- Igor

> On Jun 18, 2019, at 2:44 AM, Markus Gronlund <markus.gronlund at oracle.com> wrote:
> 
> Hi Igor,
> 
> Thank you for looking into providing this support.
> 
> This work partly overlaps with something I have been working on under the following enhancement:
> 
> Enh: https://bugs.openjdk.java.net/browse/JDK-8216041
> 
> I have had a patch somewhat semi-ready for some years now, please see:
> http://cr.openjdk.java.net/~mgronlun/8216041/
> 
> Here is what the information set could look visually by default (no structured rendering) in JDK Mission Control:
> http://cr.openjdk.java.net/~mgronlun/8216041/DeoptimizationEvent.jpg
> 
> Maybe we should merge our work for this effort (I am interested in your test case)?
> 
> I think we need to take a larger view on this, especially to see if this information could also be made understandable and maybe even useful to the end-user / developer.
> 
> This is the reason I choose to use the "deoptimization" concept instead of the more internal UncomonTrap.
> 
> Let's see if we together can craft a useful event here.
> 
> Thanks
> Markus
> 
> -----Original Message-----
> From: Igor Ignatyev 
> Sent: den 11 juni 2019 20:49
> To: hotspot-jfr-dev at openjdk.java.net; hotspot compiler <hotspot-compiler-dev at openjdk.java.net>
> Subject: RFR(S) : 8225554 : add JFR event for uncommon trap
> 
> http://cr.openjdk.java.net/~iignatyev//8225554/webrev.00/index.html
>> 187 lines changed: 184 ins; 0 del; 3 mod;
> 
> Hi all,
> 
> could you please review this small patch which adds jfr event for uncommon trap?
> 
> webrev: http://cr.openjdk.java.net/~iignatyev//8225554/webrev.00/index.html
> JBS: https://bugs.openjdk.java.net/browse/JDK-8225554
> testing:
> - tier1 (which includes a newly added test)
> - modified version of compiler/intrinsics/klass/CastNullCheckDroppingsTest.java (see JDK-8129092[1])
> 
> [1] https://bugs.openjdk.java.net/browse/JDK-8129092
> 
> Thanks,
> -- Igor