[vmkit-commits] Breaking change for openjdk

[Nicolas Geoffray]

Hi Will,

Thanks very much for the instructions! I managed to get everything working
with two gotchas:
1) libjvm.so could not be found. I had to set LD_LIBRARY_PATH to its
location.
2) Generating BootstrapClasses.s does not work on a machine with 1GB of
RAM. It did work on my 12GB work station. We might need to split it into
mulitple files.

Other than that, it worked like a charm! I did see a memory leak, but did
not investigate much. I also tried to use a generational GC but hit an MMTk
assertion quite soon. I will investigate.

FYI, here are some numbers for the dacapo benchmarks. I can't wait to
see JVM_GetClassConstantPool implemented :) And hopefully, it's not as bad
as it looks. By the name, it looks like we need to have a common
representation of the constant pool between libjava.so and vmkit.

avrora: 8490 (8103)
batik: segfault (java exception)
eclipse: java exception (java exception)
fop: 1792 (java exception)
h2: java exception (gc error)
jython: unimplemented JVM_GetClassConstantPool (unimplemented
NewWeakGlobalRef)
luindex: 2185 (2135)
lusearch: 2131 (3683)
pmd: 3473 (3526)
sunflow: 5548 (4671)
tomcat: unimplemented JVM_GetClassConstantPool (segfault)
tradebeans: unimplemented JVM_GetClassConstantPool (java exception)
tradesoap: unimplemented JVM_GetClassConstantPool (java exception)
 xalan: 21728 (2970)

Nice work!
Nicolas

On Sun, Dec 18, 2011 at 7:55 AM, Will Dietz <wdietz2 at illinois.edu> wrote:

> On Fri, Dec 2, 2011 at 11:54 AM, Nicolas Geoffray
> <nicolas.geoffray at gmail.com> wrote:
> > Yes, I believe that's possible. Depends if openjdk needs fancy things
> when
> > creating a WeakHashMap.
>
> How right you were (see commits involving hardcoding the
> java.lang.Reference's clinit as to not spawn its own thread....) but
> seems to be working fine now :).
>
> > This is great news! Does that mean precompilation and GC work on the
> openjdk
> > port? That's awesome. Can't wait to try it out!
>
> Precompilation has worked for some time (the speedups it provides
> makes it a high priority :)), and I believe the GC works.  It
> certainly "mostly" works, but for example the limiting factor in
> specjvm2008 presently is that memory isn't being freed when it should,
> so I'm running out of memory when trying to do a full run--running
> individual benchmarks works much better.  In general the bugs I'm
> seeing seem to be more of a "memory not freed" variety not a "memory
> freed that shouldn't be", which is some comfort.
>
> Also, I've almost exclusively tested with the default MarkSweep mmtk
> plan, although the others seem to work in much more limited testing.
>
> As for trying this out yourself, here's a rough guide:
>
> ** Install an OpenJDK JDK6 (not Sun, not JRE, not 1.7).
> This should be available in your linux distribution's package manager,
> otherwise I've had great success with locally built copies of icedtea6
> (what I use for most my testing, actually).
>
> ** Replace the GNU Classpath-related configure arguments with
> "--with-classpath-impl=openjdk --with-openjdk-path=$JDK_HOME".
> JDK_HOME is in surprisingly different places on different
> distributions, but it should contain "bin/javac" as well as a "jre"
> subdirectory.  The configure script's checks on the path should tell
> you if you've got the right path.
>
> ** "make"
> Might want to cross your fingers first :).
>
>
> Some caveats when testing this on the various systems I have access to:
>
> * When precompiling, in particular building BootstrapClasses.s,
> sometimes gcc (at least with 4.4.5 on one particular system) barfs
> claiming invalid assembly.  Other versions of gcc build the same
> assembly fine, and "make CC=clang CXX=clang++" avoids this as well.
> FYI
> * Many recent OpenJDK versions seem to work (1.9 and later), although
> I've encountered one ("OpenJDK Runtime Environment (IcedTea6 1.9.10)
> (rhel-1.40.1.9.10.el6_1-x86_64)" from Scientific Linux 6.1) that has
> some dlopen/dlclose issue (of all things) that makes accessing fonts
> segfault.  Previous version from same distribution works as does
> building from scratch via IcedTea, so I've mostly given up on this.
>
> The abbreviated version of the above is that "some configurations
> don't work" and I don't have a particularly great handle on that due
> to lack of time and testing :).  So YMMV.
>
> If you do get to trying it please let me know how it goes/if you have
> problems/etc :).  Once it seems to work well for you, then I can work
> towards writing a more formal set of instructions for the website as
> you previously mentioned :).
>
> Good luck and happy holidays! :)
>
> ~Will
>
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