1 files changed, 60 insertions, 3 deletions

diff --git a/src/cpu/activity.hh b/src/cpu/activity.hh
index 2d53dc4bb..2c0df5efb 100644
--- a/src/cpu/activity.hh
+++ b/src/cpu/activity.hh
@@ -1,3 +1,30 @@
+/*
+ * Copyright (c) 2006 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
 
 #ifndef __CPU_ACTIVITY_HH__
 #define __CPU_ACTIVITY_HH__
@@ -5,33 +32,61 @@
 #include "base/timebuf.hh"
 #include "base/trace.hh"
 
+/**
+ * ActivityRecorder helper class that informs the CPU if it can switch
+ * over to being idle or not.  It works by having a time buffer as
+ * long as any time buffer in the CPU, and the CPU and all of its
+ * stages inform the ActivityRecorder when they write to any time
+ * buffer.  The ActivityRecorder marks a 1 in the "0" slot of the time
+ * buffer any time a stage writes to a time buffer, and it advances
+ * its time buffer at the same time as all other stages.  The
+ * ActivityRecorder also records if a stage has activity to do next
+ * cycle.  The recorder keeps a count of these two.  Thus any time the
+ * count is non-zero, there is either communication still in flight,
+ * or activity that still must be done, meaning that the CPU can not
+ * idle.  If count is zero, then the CPU can safely idle as it has no
+ * more outstanding work to do.
+ */
 class ActivityRecorder {
   public:
     ActivityRecorder(int num_stages, int longest_latency, int count);
 
     /** Records that there is activity this cycle. */
     void activity();
-    /** Advances the activity buffer, decrementing the activityCount if active
-     *  communication just left the time buffer, and descheduling the CPU if
-     *  there is no activity.
+
+    /** Advances the activity buffer, decrementing the activityCount
+     *  if active communication just left the time buffer, and
+     *  determining if there is no activity.
      */
     void advance();
+
     /** Marks a stage as active. */
     void activateStage(const int idx);
+
     /** Deactivates a stage. */
     void deactivateStage(const int idx);
 
+    /** Returns how many things are active within the recorder. */
     int getActivityCount() { return activityCount; }
 
+    /** Sets the count to a starting value.  Can be used to disable
+     * the idling option.
+     */
     void setActivityCount(int count)
     { activityCount = count; }
 
+    /** Returns if the CPU should be active. */
     bool active() { return activityCount; }
 
+    /** Clears the time buffer and the activity count. */
     void reset();
 
+    /** Debug function to dump the contents of the time buffer. */
     void dump();
 
+    /** Debug function to ensure that the activity count matches the
+     * contents of the time buffer.
+     */
     void validate();
 
   private:
@@ -45,6 +100,7 @@ class ActivityRecorder {
      */
     TimeBuffer<bool> activityBuffer;
 
+    /** Longest latency time buffer in the CPU. */
     int longestLatency;
 
     /** Tracks how many stages and cycles of time buffer have
@@ -58,6 +114,7 @@ class ActivityRecorder {
      */
     int activityCount;
 
+    /** Number of stages that can be marked as active or inactive. */
     int numStages;
 
     /** Records which stages are active/inactive. */