Reduce counts when class of method is not in SCC

By default, OpenJ9 uses an "implicit" shared class cache (SCC)
that is used to cache "bootstrap" classes and methods.
Currently, methods whose class is not present in the SCC
receive a high initial invocation count (3000/3000 for
loopless/loopy method) in order to improve steady state
throughput. However, this could affect start-up time of
applications because methods are interpreted for too long
before being JIT compiled.
The presence of `-Xshareclasses` on the command line is a sign
that the user cares about start-up time and OpenJ9 automatically
lowers the invocations counts to 1000/250. However, with the
implicit SCC (no -Xshareclasses command line option), application
classes are not cached and methods belonging to those classes
will receive a large initial invocation count (3000/3000). Since
application classes are likely important, we would like to use
lower counts even when the implict SCC is used.

This commit lowers the initial invocation counts for methods
whose class is not in SCC under the following conditions:
- SCC is used. Rationale: -Xshareclasses:none may be a sign that
user does not care about start-up that much.
- -Xtune:throughput is not used. Rationale: this option is a
clear signal that the user cares more about throughput than startup.
- The user has not provided a specific count on the command line.
- The JVM is in start-up mode. Rationale: this feature only seeks
to improve start-up time.
- The JVM runs on 4 or more vCPUs. Rationale: lower counts will
generate more compilations which will compete with application

Depends on eclipse/omr/#7156

Signed-off-by: Marius <[email protected]>

runtime/compiler/control/HookedByTheJit.cpp

@@ -573,14 +573,29 @@ static void jitHookInitializeSendTarget(J9HookInterface * * hook, UDATA eventNum
                compInfo->setAotQueryTime(compInfo->getAotQueryTime() + (UDATA)sharedQueryTime);
                }
             }
-         else // ROM class not in shared class cache
+         else // ROM class not in shared class cache (no space or ineligible - maybe because of implicit SCC)
             {
+            // SCC is used, either explicit or implicit; this is a sign that start-up may be important
+            // If there is enough CPU power to compile sooner, do so by using lower counts
+            // but only for the classes loaded during startup
+            if (!TR::Options::getCountsAreProvidedByUser() && !countInOptionSet)
+               {
+               if (TR::Options::getCmdLineOptions()->getOption(TR_UseLowerCountsForNonSCCMethodsDuringStartup) &&
+                   (jitConfig->javaVM->phase != J9VM_PHASE_NOT_STARTUP) &&
+                   TR::Compiler->target.numberOfProcessors() >= TR_NUMPROC_FOR_LARGE_SMP)
+                  {
+                  count = getCount(romMethod, optionsJIT, optionsAOT); // counts are lower when SCC is enabled
+                  }
 #if !defined(J9ZOS390)  // Do not change the counts on zos at the moment since the
-            // shared cache capacity is higher on this platform and by
-            // increasing counts we could end up significantly impacting startup
-            if (TR::Options::getCmdLineOptions()->getOption(TR_UseHigherCountsForNonSCCMethods))
-               count = J9ROMMETHOD_HAS_BACKWARDS_BRANCHES(romMethod) ? TR_DEFAULT_INITIAL_BCOUNT : TR_DEFAULT_INITIAL_COUNT;
+                        // shared cache capacity is higher on this platform and by
+                        // increasing counts we could end up significantly impacting startup
+               else
+                  {
+                  if (TR::Options::getCmdLineOptions()->getOption(TR_UseHigherCountsForNonSCCMethods))
+                     count = J9ROMMETHOD_HAS_BACKWARDS_BRANCHES(romMethod) ? TR_DEFAULT_INITIAL_BCOUNT : TR_DEFAULT_INITIAL_COUNT;
+                  }
 #endif // !J9ZOS390
+               }
             }
 #endif // defined(J9VM_INTERP_AOT_COMPILE_SUPPORT) && defined(J9VM_OPT_SHARED_CLASSES) && (defined(TR_HOST_X86) || defined(TR_HOST_POWER) || defined(TR_HOST_S390) || defined(TR_HOST_ARM) || defined(TR_HOST_ARM64))
          } // if (TR::Options::sharedClassCache())