Instead of keeping track of the fraction of time that we're

idle, keep track of the fraction of time we're not idle.  This
works better because the default processor state is idle, and
the default stat value is 0.
Keep the stat as idleFraction which is a formula that is equal
to 1 - notIdleFraction

--HG--
extra : convert_revision : 331c2e46f45ae0abda46988567ac2c4f7c42ccad

2 files changed, 7 insertions, 4 deletions

diff --git a/cpu/simple_cpu/simple_cpu.cc b/cpu/simple_cpu/simple_cpu.cc
index 4b9a7c6bd..aaf8a9dc5 100644
--- a/cpu/simple_cpu/simple_cpu.cc
+++ b/cpu/simple_cpu/simple_cpu.cc
@@ -247,7 +247,7 @@ SimpleCPU::setStatus(Status new_status)
 
       case Idle:
         assert(old_status == Running);
-        idleFraction++;
+        notIdleFraction--;
         if (tickEvent.scheduled())
             tickEvent.squash();
         break;
@@ -256,8 +256,8 @@ SimpleCPU::setStatus(Status new_status)
         assert(old_status == Idle ||
                old_status == DcacheMissStall ||
                old_status == IcacheMissComplete);
-        if (old_status == Idle && curTick != 0)
-            idleFraction--;
+        if (old_status == Idle)
+            notIdleFraction++;
 
         if (tickEvent.squashed())
             tickEvent.reschedule(curTick + 1);
@@ -304,6 +304,7 @@ SimpleCPU::regStats()
         .prereq(dcacheStallCycles)
         ;
 
+    idleFraction = constant(1.0) - notIdleFraction;
     numInsts = Statistics::scalar(numInst) - Statistics::scalar(startNumInst);
     simInsts += numInsts;
 }
@@ -312,6 +313,7 @@ void
 SimpleCPU::resetStats()
 {
     startNumInst = numInst;
+    notIdleFraction = (_status != Idle);
 }
 
 void
diff --git a/cpu/simple_cpu/simple_cpu.hh b/cpu/simple_cpu/simple_cpu.hh
index e497559ce..666fe490b 100644
--- a/cpu/simple_cpu/simple_cpu.hh
+++ b/cpu/simple_cpu/simple_cpu.hh
@@ -193,7 +193,8 @@ class SimpleCPU : public BaseCPU
     Counter startNumLoad;
 
     // number of idle cycles
-    Statistics::Average<> idleFraction;
+    Statistics::Average<> notIdleFraction;
+    Statistics::Formula idleFraction;
 
     // number of cycles stalled for I-cache misses
     Statistics::Scalar<> icacheStallCycles;