RFR (XL) 8046070 - Class Data Sharing clean up and refactoring, round #2

[Ioi Lam]

On 8/7/14, 1:48 AM, Florian Weimer wrote:
> On 07/29/2014 01:09 AM, Ioi Lam wrote:
>> Hi Folks,
>>
>> Please review the following clean up and refactoring of the CDS code,
>> for JDK9
>>
>>      http://cr.openjdk.java.net/~iklam/8046070-cds-cleanup-v2/
>> https://bugs.openjdk.java.net/browse/JDK-8046070
>
> Can you check if this bit in 
> hotspot/src/share/vm/runtime/arguments.cpp is still up-to-date?
>
> 1566 #ifdef COMPILER2
> 1567   // Shared spaces work fine with other GCs but causes bytecode 
> rewriting
> 1568   // to be disabled, which hurts interpreter performance and 
> decreases
> 1569   // server performance.  When -server is specified, keep the 
> default off
> 1570   // unless it is asked for.  Future work: either add bytecode 
> rewriting
> 1571   // at link time, or rewrite bytecodes in non-shared methods.
> 1572   if (!DumpSharedSpaces && !RequireSharedSpaces &&
> 1573       (FLAG_IS_DEFAULT(UseSharedSpaces) || !UseSharedSpaces)) {
> 1574     no_shared_spaces("COMPILER2 default: -Xshare:auto | off, have 
> to manually setup to on.");
> 1575   }
> 1576 #endif
>
Unfortunately this is still true. I think there's a bug on this and we 
don't have time to address that within this patch.
> I think with tiered compilation, the server VM should suffer less from 
> the lack of bytecode rewriting because early C1 compilation reduces 
> the dependency on interpreter performance.  Or is this not true?
>
It might help, but I have not run any benchmarks to verify this.

Thanks
- Ioi
> Thanks,
> Florian