8255047: Add HotSpot UseDebuggerErgo flags

Reviewed-by: dcubed, dholmes

Author: stefank

src/hotspot/os/linux/globals_linux.hpp

@@ -79,7 +79,7 @@
           "be dumped into the corefile.")                               \
                                                                         \
   product(bool, UseCpuAllocPath, false, DIAGNOSTIC,                     \
-             "Use CPU_ALLOC code path in os::active_processor_count ")
+          "Use CPU_ALLOC code path in os::active_processor_count ")
 
 // end of RUNTIME_OS_FLAGS
 

src/hotspot/os/linux/os_linux.cpp

@@ -3217,7 +3217,17 @@ void os::Linux::rebuild_cpu_to_node_map() {
         if (cpu_map[j] != 0) {
           for (size_t k = 0; k < BitsPerCLong; k++) {
             if (cpu_map[j] & (1UL << k)) {
-              cpu_to_node()->at_put(j * BitsPerCLong + k, closest_node);
+              int cpu_index = j * BitsPerCLong + k;
+
+#ifndef PRODUCT
+              if (UseDebuggerErgo1 && cpu_index >= (int)cpu_num) {
+                // Some debuggers limit the processor count without
+                // intercepting the NUMA APIs. Just fake the values.
+                cpu_index = 0;
+              }
+#endif
+
+              cpu_to_node()->at_put(cpu_index, closest_node);
             }
           }
         }
@@ -4762,7 +4772,16 @@ int os::active_processor_count() {
 
 uint os::processor_id() {
   const int id = Linux::sched_getcpu();
-  assert(id >= 0 && id < _processor_count, "Invalid processor id");
+
+#ifndef PRODUCT
+  if (UseDebuggerErgo1 && id >= _processor_count) {
+    // Some debuggers limit the processor count without limiting
+    // the returned processor ids. Fake the processor id.
+    return 0;
+  }
+#endif
+
+  assert(id >= 0 && id < _processor_count, "Invalid processor id [%d]", id);
   return (uint)id;
 }
 

src/hotspot/share/runtime/arguments.cpp

@@ -3901,6 +3901,22 @@ bool Arguments::handle_deprecated_print_gc_flags() {
   return true;
 }
 
+static void apply_debugger_ergo() {
+  if (UseDebuggerErgo) {
+    // Turn on sub-flags
+    FLAG_SET_ERGO_IF_DEFAULT(UseDebuggerErgo1, true);
+    FLAG_SET_ERGO_IF_DEFAULT(UseDebuggerErgo2, true);
+  }
+
+  if (UseDebuggerErgo2) {
+    // Debugging with limited number of CPUs
+    FLAG_SET_ERGO_IF_DEFAULT(UseNUMA, false);
+    FLAG_SET_ERGO_IF_DEFAULT(ConcGCThreads, 1);
+    FLAG_SET_ERGO_IF_DEFAULT(ParallelGCThreads, 1);
+    FLAG_SET_ERGO_IF_DEFAULT(CICompilerCount, 2);
+  }
+}
+
 // Parse entry point called from JNI_CreateJavaVM
 
 jint Arguments::parse(const JavaVMInitArgs* initial_cmd_args) {
@@ -4097,6 +4113,8 @@ jint Arguments::parse(const JavaVMInitArgs* initial_cmd_args) {
   }
 #endif
 
+  apply_debugger_ergo();
+
   return JNI_OK;
 }
 

src/hotspot/share/runtime/globals.hpp

@@ -2207,6 +2207,17 @@ const intx ObjectAlignmentInBytes = 8;
   product(bool, UseNewCode3, false, DIAGNOSTIC,                             \
           "Testing Only: Use the new version while testing")                \
                                                                             \
+  notproduct(bool, UseDebuggerErgo, false,                                  \
+          "Debugging Only: Adjust the VM to be more debugger-friendly. "    \
+          "Turns on the other UseDebuggerErgo* flags")                      \
+                                                                            \
+  notproduct(bool, UseDebuggerErgo1, false,                                 \
+          "Debugging Only: Enable workarounds for debugger induced "        \
+          "os::processor_id() >= os::processor_count() problems")           \
+                                                                            \
+  notproduct(bool, UseDebuggerErgo2, false,                                 \
+          "Debugging Only: Limit the number of spawned JVM threads")        \
+                                                                            \
   /* flags for performance data collection */                               \
                                                                             \
   product(bool, UsePerfData, true,                                          \