Java Performance Degradation in JDK7 and JDK8

Maurizio Cimadamore maurizio.cimadamore at
Wed Apr 29 10:00:45 UTC 2015

These are the numbers I'm getting:

JDK 9 (b42)

Note: generated_ttcn/ uses or overrides a 
deprecated API.
Note: Recompile with -Xlint:deprecation for details.

real    0m46.306s
user    2m17.489s
sys    0m2.166s

JDK 8 (GA)

Note: generated_ttcn/ uses or overrides a 
deprecated API.
Note: Recompile with -Xlint:deprecation for details.

real    6m58.748s
user    8m43.546s
sys    0m2.132s

JDK 7 (1.7.0_79)

Note: generated_ttcn/ uses or overrides a 
deprecated API.
Note: Recompile with -Xlint:deprecation for details.

real    0m28.341s
user    1m17.194s
sys    0m1.886s

As you can see there is a significant regression from JDK 7 to JDK 8 
which was caused by

(some stack trace analysis revealed the familiar pattern). This has also 
been fixed in JDK 8u20 (as stated in the bug evaluation).

So, while JDK 8u20/9 is slower than JDK 7 (at least on my machine), the 
numbers are more or less in the same ballpark and the huge regression 
that was visible in earlier JDK 8 releases has now been fixed.

If you are still experiencing the problem - can you please also submit 
the specific compiler versions you are using in your benchmark?


On 29/04/15 10:29, Maurizio Cimadamore wrote:
> Hi Jacob,
> Stay assured - as we'll definitively look into this issue (I see it's 
> already assigned to one of my colleagues).
> What I can say (w/o looking too much at the attached artifacts) is 
> that in general, javac has no issue with compiling a lot of sources at 
> once; at one point the build system was structured in such a way that 
> all the JDK classes were compiled at once - and that (which is way 
> more than your 187 sources - i.e. at least 10x that) took less than 20 
> seconds. SO there must some specific pattern triggering that issue.
> Given that you say you have 187 input sources and 48K output classes, 
> I'd say you are using inner classes a lot. I wonder if you are hitting 
> this:
> Maurizio
> On 24/04/15 09:49, Jacob Wieland wrote:
>> Hello Folks,
>> I still have the open problem 
>> that the javac 
>> performance has degraded significantly from 1.6 to 1.7 (and even 
>> worse to 1.8) in the 64bit versions. Since in our context, we are 
>> dealing with a lot of generated source1.4 Java input (either split 
>> into very large files with inner classes or big packages with lots of 
>> smaller classes), compiler performance is critical for our tool and 
>> this degradation forces us to continue recommending to our customers 
>> to use Java 1.6 for large projects (as is the norm) as 1.7 and 1.8 
>> are pretty much unusable in this respect.
>> Is anyone still working on this issue or is such significant 
>> performance degradation not a serious issue?
>> My observations so far are:
>> - it gets worse the more class files are being compiled/the more 
>> files reside in the source path
>> - cpu usage goes through the roof over all available kernels
>> - memory usage is much higher
>> - garbage collection seems to be much more active
>> Using -proc:none alleviates the problem slightly for the 1.7 version, 
>> but not for 1.8 (last we tested with jdk1.8.0_31) where the 
>> performance difference is a factor 5 or more!
>> I can understand that a more advanced compiler has capabilities that 
>> a previous version does not have and thus sometimes has
>> to do more work. But, it should still be possible (especially if 
>> given the -source 1.4 or -source 1.5 option as we do) to optimize it 
>> in such a way that unnecessary checks for generics, overriding 
>> methods, closures, annotations and other newer features can be turned 
>> off (if they are to blame, which I actually doubt from my observations).
>> I would really appreciate your help in this regard and I think 
>> everyone would benefit from any bugfix you can offer for this.
>> BR, Jacob Wieland
>> -- 
>> -- 
>> ------------------------------
>> -------------------------------------------
>> Dr. Jacob Wieland
>> Senior Software Engineer
>> Testing Technologies IST GmbH
>> Michaelkirchstraße 17/18
>> 10179 Berlin, Germany
>> Phone +49 30 726 19 19 34 Email wieland at 
>> <mailto:stanca at>
>> Fax +49 30 726 19 19 20  Internet 
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