On 30.11.2017 14:42, Emmanuel Bourg wrote:
Le 30/11/2017 à 10:27, dalibor topic a écrit :
Thanks, Emmanuel - in many of these cases (AspectJ, ICU, Spotbugs,
Gradle, Scala) the way forward seems to be to upgrade the packaged
software to the latest upstream version supporting JDK 9, often thanks
to the patches provided by Chris West and the related efforts to rebuild
the Debian archive with JDK 9 early access builds.
Easier said than done unfortunately ;)
Sadly, yeah.
My humble suggestion would be to never deprecate the old source/target
levels.
I understand the sentiment. Unfortunately, that would steadily increase
the maintenance cost of the compiler, while the potential benefit of
supporting old source/target levels would steadily decrease, since most
compiler users don't use it to recompile very old sources code with very
new JDKs.
The new annoyance with javadoc in OpenJDK 9 is the increased severity of
incomplete classpaths. Before javadoc would just complain, now it stops
with an error. We can work around that with the -old parameter, but it
doesn't work with OpenJDK 8.
That won't work with 10 either, unfortunately, since the old doclet has
(finally) been removed. Please see
https://bugs.openjdk.java.net/browse/JDK-8177511 for details.
I personally don't understand why JAF is being removed. This barely
saves 80KB in the JDK, it could have stayed there, no one would have
complained.
In contrast to many third party libraries, the JDK has a very regular
release cycle, leading to four or more releases per year. Code that we
don't need to distribute as part of OpenJDK 10, 11, etc is not code we
have to patch, maintain and update as part of the regular JDK release
cycle.
Carrying code in the JDK that the JDK itself does not use carries both a
maintenance cost (we now also need to address the technical debt in X),
and increases the complexity of design decisions (how should the design
of a feature interacting with X be if someone uses the JDK version of X,
rather than the upstream version of X).
It requires running java with -Xshare:dump on installation. See
https://mjg123.github.io/2017/10/02/JVM-startup.html for an example and
https://mjg123.github.io/2017/10/04/AppCDS-and-Clojure.html for an
example using AppCDS.
Thanks for the reference. I tried the clojure example with our openjdk-8
and openjdk-9 packages but didn't measure a significant difference in
execution time. Does it depend on recent kernel features?
It shouldn't, though ASLR may play a role - what does
-Xlog:class+load=info say?
cheers,
dalibor topic
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