building libjvm with -Os for space optimization - was : RE: RFR: 8234525: enable link-time section-gc for linux s390x to remove unused code

[Magnus Ihse Bursie]

On 2019-12-18 00:05, August Nagro wrote:
> I published some benchmarks of OpenJDK on Mac with Ofast and O3 [1]. Some microbenchmarks like Netty’s HttpObjectEncoder experienced >100% speedup with O3, and the more real-world Dacapo suite was ~15% improvement over O2 (which is exactly the same as Os). I did include a few other flags, however the speedup was primarily due to optimization level.
>
> Building with Os is the old wisdom. It used to be the case that many programs would be faster with the smaller binary size, but this is almost never the case nowadays.
>
> - August
>
> [1]: http://august.nagro.us/optimized-openjdk.html
Nice. :)

I noticed this on your blog post:
> I also tried building withIntel’s Compiler 
> <https://software.intel.com/en-us/c-compilers>, and patched the 
> configure scripts to allow it. However, the build failed cryptically. 
> I’d also be interested to see Linux results.

How did you patch configure, and what errors did you run into? In 
general, it's not a small task to get OpenJDK to compile with a new 
compiler, but Intel claims a high level of compatibility with gcc [1] 
and that increases chances that it should be possible to achieve with 
not too much effort. I'm slightly tempted to looking into it. :)

/Magnus

[1] 
https://software.intel.com/en-us/cpp-compiler-developer-guide-and-reference-gcc-compatibility-and-interoperability