8255756: Disabling logging does unnecessary work

Reviewed-by: iklam

src/hotspot/share/logging/logConfiguration.cpp

@@ -110,9 +110,7 @@ void LogConfiguration::initialize(jlong vm_start_time) {
 }
 
 void LogConfiguration::finalize() {
-  for (size_t i = _n_outputs; i > 0; i--) {
-    disable_output(i - 1);
-  }
+  disable_outputs();
   FREE_C_HEAP_ARRAY(LogOutput*, _outputs);
 }
 
@@ -272,28 +270,31 @@ void LogConfiguration::configure_output(size_t idx, const LogSelectionList& sele
   assert(strlen(output->config_string()) > 0, "should always have a config description");
 }
 
-void LogConfiguration::disable_output(size_t idx) {
-  assert(idx < _n_outputs, "invalid index: " SIZE_FORMAT " (_n_outputs: " SIZE_FORMAT ")", idx, _n_outputs);
-  LogOutput* out = _outputs[idx];
+void LogConfiguration::disable_outputs() {
+  size_t idx = _n_outputs;
 
-  // Remove the output from all tagsets.
+  // Remove all outputs from all tagsets.
   for (LogTagSet* ts = LogTagSet::first(); ts != NULL; ts = ts->next()) {
-    ts->set_output_level(out, LogLevel::Off);
-    ts->update_decorators();
+    ts->disable_outputs();
   }
 
-  // Delete the output unless stdout or stderr (idx 0 or 1)
-  if (idx > 1) {
-    delete_output(idx);
-  } else {
-    out->set_config_string("all=off");
+  while (idx > 0) {
+    LogOutput* out = _outputs[--idx];
+    // Delete the output unless stdout or stderr (idx 0 or 1)
+    if (idx > 1) {
+      delete_output(idx);
+    } else {
+      out->set_config_string("all=off");
+    }
   }
 }
 
 void LogConfiguration::disable_logging() {
   ConfigurationLock cl;
-  for (size_t i = _n_outputs; i > 0; i--) {
-    disable_output(i - 1);
+  disable_outputs();
+  // Update the decorators on all tagsets to get rid of unused decorators
+  for (LogTagSet* ts = LogTagSet::first(); ts != NULL; ts = ts->next()) {
+    ts->update_decorators();
   }
   notify_update_listeners();
 }

src/hotspot/share/logging/logConfiguration.hpp

@@ -69,8 +69,8 @@ class LogConfiguration : public AllStatic {
   // Output should be completely disabled before it is deleted.
   static void delete_output(size_t idx);
 
-  // Disable all logging to the specified output and then delete it (unless it is stdout/stderr).
-  static void disable_output(size_t idx);
+  // Disable all logging to all outputs. All outputs except stdout/stderr will be deleted.
+  static void disable_outputs();
 
   // Get output index by name. Returns SIZE_MAX if output not found.
   static size_t find_output(const char* name);

src/hotspot/share/logging/logOutputList.cpp

@@ -68,6 +68,25 @@ LogOutputList::LogOutputNode* LogOutputList::find(const LogOutput* output) const
   return NULL;
 }
 
+void LogOutputList::clear() {
+
+  // Grab the linked list
+  LogOutputNode* cur = _level_start[LogLevel::Last];
+
+  // Clear _level_start
+  for (uint level = LogLevel::First; level < LogLevel::Count; level++) {
+    _level_start[level] = NULL;
+  }
+
+  // Delete all nodes from the linked list
+  wait_until_no_readers();
+  while (cur != NULL) {
+    LogOutputNode* next = cur->_next;
+    delete cur;
+    cur = next;
+  }
+}
+
 void LogOutputList::remove_output(LogOutputList::LogOutputNode* node) {
   assert(node != NULL, "Node must be non-null");
 

src/hotspot/share/logging/logOutputList.hpp

@@ -88,6 +88,10 @@ class LogOutputList {
   // Set (add/update/remove) the output to the specified level.
   void set_output_level(LogOutput* output, LogLevelType level);
 
+  // Removes all outputs. Equivalent of set_output_level(out, Off)
+  // for all outputs.
+  void clear();
+
   class Iterator {
     friend class LogOutputList;
    private:

src/hotspot/share/logging/logTagSet.hpp

@@ -98,6 +98,10 @@ class LogTagSet {
     return _output_list.level_for(output);
   }
 
+  void disable_outputs() {
+    _output_list.clear();
+  }
+
   void set_output_level(LogOutput* output, LogLevelType level) {
     _output_list.set_output_level(output, level);
   }