Disable GCR for hot compilations

GCR (guarded counting recompilations is a mechanism that is supposed to upgrade cold or AOT compilations to warm opt level. In theory it should work with any opt level, but due to a bug it seems that GCR is incompatible with hot compilations (see eclipse-openj9#4548 for details). To allow stress testing with hot compilations this commit disables GCR for hot compilations. This should have no bearing on behavior in production because the natural way of upgrading hot compilations to scorching is through sampling. Fixes: eclipse-openj9#4445 eclipse-openj9#8064 Signed-off-by: Marius Pirvu <[email protected]>
mpirvu · May 7, 2020 · 4191168 · 4191168
1 parent 5f4a9c9
commit 4191168
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/runtime/compiler/control/CompilationThread.cpp b/runtime/compiler/control/CompilationThread.cpp
@@ -8332,9 +8332,10 @@ TR::CompilationInfoPerThreadBase::wrappedCompile(J9PortLibrary *portLib, void *
                      options->setOption(TR_UseSymbolValidationManager, false);
                   }
 
-               // See if we need to inset GCR trees
-               if (!details.supportsInvalidation())
-                  {
+               // See if we need to insert GCR trees
+               if (!details.supportsInvalidation() ||
+                   options->getOptLevel() >= hot) // Workaround for a bug with GCR inserted in hot bodies. See #4549 for details.
+                  {                               // Upgrades hot-->scorching should be done through sampling, not GCR
                   options->setOption(TR_DisableGuardedCountingRecompilations);
                   }
                else if (vm->isAOT_DEPRECATED_DO_NOT_USE() || (options->getOptLevel() < warm &&