Compiling libjvm.so as PIC

[Andrew Haley]

Omair Majid wrote:
> Matthias Klose wrote:
>> Omair Majid schrieb:
>>> Ionana and I have been trying to get icedtea to work when built as a
>>> normal user with SELinux enabled. SELinux stops java from loading
>>> libjvm.so which is built as non-PIC. Please see
>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6538311 for more
>>> information.
>>>
>>> The bug report states that building libjvm.so as PIC has performance
>>> penalties. Ioana and I have been comparing the performance of a JVM
>>> built as PIC with one built as non-PIC for the last few days. For the
>>> JVM built as PIC, the fastest run was about 3% faster than the slowest.
>>> For the JVM built as non-PIC, the fastest run was about 1% faster than
>>> the slowest. Comparing the average performance, the PIC JVM seems to be
>>> faster by 0.59% which indicates that any difference in performance is
>>> negligible.
>>>
>>> Building libjmv.so as PIC should also result in memory savings as the
>>> code segment will be shared across processes.
>>>
>>> The attached patch will build libjvm.so as PIC. Any objections to
>>> applying it?
>>
>> does it make a difference with SELinux disabled?
> 
> I just finished running the tests with SELinux disabled. The performance
> difference between a PIC jvm and a non-PIC jvm was about 0.9%, with the
> PIC jvm being actually faster. So any performance loss is negligible.

Thanks.  I suspect that the problem this non-PIC compile was supposed to fix
may be a bit of ancient history based on an old version of gcc.  It's not
entirely surprising that PIC might be faster, since fixing up the non-PIC
relocations takes extra time.

I think you proved your point and should check this change in.

Andrew.