EVALUATION

http://hg.openjdk.java.net/hsx/hsx16/master/rev/4385d4e7497b
                                     

PUBLIC COMMENTS

The same assert might be hit with -XX:+UnlockDiagnosticVMOptions -XX:+Verify{Before,After}GC.
The workaround of -Xshare:off documented in the "Workaround" field would work around the issue(s),
but end up turning off class data sharing.
                                     

WORK AROUND

-Xshare:off
                                     

EVALUATION

http://hg.openjdk.java.net/hsx/hsx16/baseline/rev/4385d4e7497b
                                     

EVALUATION

http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/26f1542097f1
                                     

SUGGESTED FIX

http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/26f1542097f1
                                     

EVALUATION

Regression in behaviour happened as a result of a latent bug that pre-existed
hs15b01, but was uncovered as a result of the changes in 6689653. See comments section for more detail.
                                     

EVALUATION

This CR will be minimally fixed to attend to the regression, and a separate
one filed to rationalize the structure of CDS to prevent the recurrence
of similar errors in the future.
                                     

EVALUATION

Filed 6897789 for cleaning up CDS/perm structuring.
                                     

EVALUATION

As in suggested fix section. Need some archeology to see why this started
showing up now, but looks like it would be a day-one bug because of the
"ShouldNotReachHere()". Will update re history.
                                     

SUGGESTED FIX

diff -r 29adffcb6a61 src/share/vm/memory/compactingPermGenGen.cpp
--- a/src/share/vm/memory/compactingPermGenGen.cpp      Fri Oct 30 13:31:11 2009 -0400
+++ b/src/share/vm/memory/compactingPermGenGen.cpp      Mon Nov 02 10:22:28 2009 -0800
@@ -352,15 +352,13 @@ void CompactingPermGenGen::post_compact(
 }
 
 
+// Do not use in time-critical operations due to the possibility of paging.
 void CompactingPermGenGen::space_iterate(SpaceClosure* blk, bool usedOnly) {
   OneContigSpaceCardGeneration::space_iterate(blk, usedOnly);
   if (spec()->enable_shared_spaces()) {
-#ifdef PRODUCT
     // Making the rw_space walkable will page in the entire space, and
-    // is to be avoided. However, this is required for Verify options.
-    ShouldNotReachHere();
-#endif
-
+    // is to be avoided. However, this is required for Verify and
+    // heap dump operations.
     blk->do_space(ro_space());
     blk->do_space(rw_space());
   }
                                     

EVALUATION

Started failing starting with hs15b01. No clue as yet which specific change
in hs15b01 caused this to start failing. Still investigating.
                                     

EVALUATION

See comments and suggested fix section.
                                     

SUGGESTED FIX

Delete lines 358-362 below, or if you don't like that, replace
ShouldNotReachHere() with return; I personally think that
performance-sensitive code should either deliberately skip over the
shared space if it wants to, rather than use this whimsical
method of preventing the use of a legitimate interface for
other purposes:-

   355  void CompactingPermGenGen::space_iterate(SpaceClosure* blk, bool usedOnly) {
   356    OneContigSpaceCardGeneration::space_iterate(blk, usedOnly);
   357    if (spec()->enable_shared_spaces()) {
   358  #ifdef PRODUCT
   359      // Making the rw_space walkable will page in the entire space, and
   360      // is to be avoided. However, this is required for Verify options.
   361      ShouldNotReachHere();
   362  #endif
   363
   364      blk->do_space(ro_space());
   365      blk->do_space(rw_space());
   366    }
   367  }
   368