JBR-7457 Provide JBR API method to explicitly call gc()

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -1849,6 +1849,13 @@ bool G1CollectedHeap::try_collect_fullgc(GCCause::Cause cause,
                                          const G1GCCounters& counters_before) {
   assert_heap_not_locked();
 
+  if (cause == GCCause::_jbr_gc_run) {
+    VM_G1CollectForAllocation op(0, // no following allocation
+                                 counters_before.total_collections(),
+                                 cause);
+    VMThread::execute(&op);
+  }
+
   while(true) {
     VM_G1CollectFull op(counters_before.total_collections(),
                         counters_before.total_full_collections(),

src/hotspot/share/gc/g1/g1VMOperations.cpp

@@ -51,8 +51,13 @@ bool VM_G1CollectFull::skip_operation() const {
 void VM_G1CollectFull::doit() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   GCCauseSetter x(g1h, _gc_cause);
-  _gc_succeeded = g1h->do_full_collection(false /* clear_all_soft_refs */,
-                                          false /* do_maximal_compaction */);
+  if (_gc_cause == GCCause::_jbr_gc_run) {
+    _gc_succeeded = g1h->do_full_collection(true /* clear_all_soft_refs */,
+                                            true /* do_maximal_compaction */);
+  } else {
+    _gc_succeeded = g1h->do_full_collection(false /* clear_all_soft_refs */,
+                                            false /* do_maximal_compaction */);
+  }
 }
 
 VM_G1TryInitiateConcMark::VM_G1TryInitiateConcMark(uint gc_count_before,

src/hotspot/share/gc/serial/serialHeap.cpp

@@ -22,6 +22,7 @@
  *
  */
 
+#include "gc/shared/gcCause.hpp"
 #include "precompiled.hpp"
 #include "classfile/classLoaderDataGraph.hpp"
 #include "classfile/stringTable.hpp"
@@ -431,7 +432,8 @@ HeapWord* SerialHeap::mem_allocate(size_t size,
 
 bool SerialHeap::must_clear_all_soft_refs() {
   return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||
-         _gc_cause == GCCause::_wb_full_gc;
+         _gc_cause == GCCause::_wb_full_gc ||
+         _gc_cause == GCCause::_jbr_gc_run;
 }
 
 bool SerialHeap::is_young_gc_safe() const {

src/hotspot/share/gc/shared/gcCause.cpp

@@ -126,6 +126,9 @@ const char* GCCause::to_string(GCCause::Cause cause) {
     case _last_gc_cause:
       return "ILLEGAL VALUE - last gc cause - ILLEGAL VALUE";
 
+    case _jbr_gc_run:
+      return "JBR full GC";
+
     default:
       return "unknown GCCause";
   }

src/hotspot/share/gc/shared/gcCause.hpp

@@ -72,6 +72,7 @@ class GCCause : public AllStatic {
     _g1_periodic_collection,
 
     _dcmd_gc_run,
+    _jbr_gc_run,
 
     _shenandoah_stop_vm,
     _shenandoah_allocation_failure_evac,
@@ -90,7 +91,8 @@ class GCCause : public AllStatic {
 
   inline static bool is_user_requested_gc(GCCause::Cause cause) {
     return (cause == GCCause::_java_lang_system_gc ||
-            cause == GCCause::_dcmd_gc_run);
+            cause == GCCause::_dcmd_gc_run ||
+            cause == GCCause::_jbr_gc_run);
   }
 
   inline static bool is_explicit_full_gc(GCCause::Cause cause) {

src/hotspot/share/gc/z/zCollectedHeap.cpp

@@ -191,6 +191,7 @@ void ZCollectedHeap::collect(GCCause::Cause cause) {
   case GCCause::_wb_full_gc:
   case GCCause::_wb_breakpoint:
   case GCCause::_dcmd_gc_run:
+  case GCCause::_jbr_gc_run:
   case GCCause::_java_lang_system_gc:
   case GCCause::_full_gc_alot:
   case GCCause::_jvmti_force_gc:

src/hotspot/share/gc/z/zDriver.cpp

@@ -236,6 +236,7 @@ static bool should_clear_all_soft_references(GCCause::Cause cause) {
   case GCCause::_wb_full_gc:
   case GCCause::_metadata_GC_clear_soft_refs:
   case GCCause::_z_allocation_stall:
+  case GCCause::_jbr_gc_run:
     return true;
 
   case GCCause::_heap_dump:
@@ -276,6 +277,7 @@ static bool should_preclean_young(GCCause::Cause cause) {
   case GCCause::_wb_full_gc:
   case GCCause::_wb_breakpoint:
   case GCCause::_dcmd_gc_run:
+  case GCCause::_jbr_gc_run:
   case GCCause::_java_lang_system_gc:
   case GCCause::_full_gc_alot:
   case GCCause::_jvmti_force_gc:
@@ -338,6 +340,7 @@ void ZDriverMajor::collect(const ZDriverRequest& request) {
   case GCCause::_heap_inspection:
   case GCCause::_wb_full_gc:
   case GCCause::_dcmd_gc_run:
+  case GCCause::_jbr_gc_run:
   case GCCause::_java_lang_system_gc:
   case GCCause::_full_gc_alot:
   case GCCause::_jvmti_force_gc:

src/hotspot/share/prims/jni.cpp

@@ -540,7 +540,11 @@ JNI_ENTRY(jint, jni_ThrowNew(JNIEnv *env, jclass clazz, const char *message))
   } else if (name->equals("java/lang/Exception$JB$$Event")) {
       Events::log(THREAD, "%s", message);
       return 0;
+  } else if (name->equals("java/lang/Exception$JB$$FullGC")) {
+    Universe::heap()->collect(GCCause::_jbr_gc_run);
+    return 0;
   }
+
   Handle class_loader (THREAD,  k->class_loader());
   THROW_MSG_LOADER_(name, (char *)message, class_loader, JNI_OK);
   ShouldNotReachHere();

src/hotspot/share/prims/jniCheck.cpp

@@ -505,6 +505,12 @@ void jniCheck::validate_throwable_klass(JavaThread* thr, Klass* klass) {
   ASSERT_OOPS_ALLOWED;
   assert(klass != nullptr, "klass argument must have a value");
 
+  if (klass->name()->index_of_at(0, "/Exception$JB$$", strlen("/Exception$JB$$")) > 0) {
+    // This is a special "marker" class that is never really thrown and
+    // therefore it does not have to be Throwable.
+    return;
+  }
+
   if (!klass->is_instance_klass() ||
       !klass->is_subclass_of(vmClasses::Throwable_klass())) {
     ReportJNIFatalError(thr, fatal_class_not_a_throwable_class);

src/java.base/share/classes/java/lang/Exception.java

@@ -125,4 +125,5 @@ protected Exception(String message, Throwable cause,
 
     private static class JB$$Assertion {}
     private static class JB$$Event {}
+    private static class JB$$FullGC {}
 }

src/java.base/share/classes/java/lang/System.java

@@ -61,6 +61,7 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Stream;
 
+import com.jetbrains.exported.JBRApi;
 import jdk.internal.javac.Restricted;
 import jdk.internal.loader.NativeLibraries;
 import jdk.internal.logger.LoggerFinderLoader.TemporaryLoggerFinder;
@@ -2339,4 +2340,7 @@ public boolean bytesCompatible(String string, Charset charset) {
             }
         });
     }
+
+    @JBRApi.Provides("SystemUtils#fullGC")
+    private static native void $$jb$FullGC();
 }

src/java.base/share/native/libjava/System.c

@@ -322,3 +322,16 @@ Java_java_lang_System_mapLibraryName(JNIEnv *env, jclass ign, jstring libname)
 
     return (*env)->NewString(env, chars, len);
 }
+
+JNIEXPORT void JNICALL
+Java_java_lang_System__00024_00024jb_00024FullGC(JNIEnv *env, jclass ign)
+{
+    jclass cls = (*env)->FindClass(env, "java/lang/Exception$JB$$FullGC");
+    if (cls != 0) {
+        // Throwing an exception by this name will trigger a full GC with 
+        // a special cause indicating the need to collect as much as possible
+        // for testing purposes.
+        (*env)->ThrowNew(env, cls, NULL);
+    }
+}
+

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/shared/GCCause.java

@@ -54,6 +54,7 @@ public enum GCCause {
   _g1_periodic_collection ("G1 Periodic Collection"),
 
   _dcmd_gc_run ("Diagnostic Command"),
+  _jbr_gc_run("JBR full GC"),
 
   _shenandoah_allocation_failure_evac ("Allocation Failure During Evacuation"),
   _shenandoah_stop_vm ("Stopping VM"),