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

Florian Weimer fweimer at redhat.com
Thu Aug 7 08:48:43 UTC 2014

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 
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 
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

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?

Florian Weimer / Red Hat Product Security

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