RFR: 8216303: JFR: Simplify generated files

[Erik Gahlin]

Hello Erik, 

> On 28 May 2020, at 19:47, Erik Joelsson <erik.joelsson at oracle.com> wrote:
> 
> Hello Erik,
> 
> I noticed that you added an import for java.util.HashSet, but it doesn't seem to be used.

Fixed.

> You also replaced the only use of HashMap with LinkedHashMap, which we like as it gives a predictable iteration order, but forgot to remove the import.
> 
> Do you know if the generated files are stable over several builds?

They should be stable. Events are numbered after how they are specified in /hotspot/share/jfr/metadata/metadata.xml.

Erik

> 
> /Erik
> 
> On 2020-05-28 10:37, Erik Gahlin wrote:
>> Hi,
>> 
>> Could I have a review of a fix that removes legacy in the generated JFR event files, in particular hard coded numbers for type / event IDs. Event IDs are now numbered from zero, which has the benefit that most of them can be represented as a single byte instead of two. This will reduce the size of recordings with a few percent.
>> 
>> I’m looping in build-dev, since I am modifying make/src/classes/build/tools/jfr/GenerateJfrFiles.java, but there are no changes to how things are built. The generated JFR files are just slightly different.
>> 
>> Old and new files:
>> http://cr.openjdk.java.net/~egahlin/8216303_generated/
>> 
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8216303
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~egahlin/8216303/
>> 
>> Testing:
>> - Building with and without jfr the feature enabled
>> - Tier 1/2 (Mac, Linux and Windows)
>> - JFR tests in test/jdk/jdk/jfr
>> 
>> Thanks
>> Erik
>> 
>>