Adding a basic interface and implementation to the Segment/Block

path to update the LRU statistics when the PageTableManager code
clears the reference bit.  This is not meant to be a complete
implementation (different Task is open for that).

This is Task 3400.

Change-Id: If67efd16ead6f68a74f5f5a698013c1b852864d9
Reviewed-on: http://gfw160.austin.ibm.com:8080/gerrit/231
Tested-by: Jenkins Server
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/src/include/kernel/spte.H b/src/include/kernel/spte.H
index 1a284d6e7..abd81dff3 100644
--- a/src/include/kernel/spte.H
+++ b/src/include/kernel/spte.H
@@ -66,8 +66,11 @@ class ShadowPTE
                     /** Allocate from a zero'd page. */
                 uint32_t allocate_from_zero:1;
 
+                    /** LRU value - lower means it was accessed more recently. */
+                uint32_t last_access:3;
+
                     /** Reserved for future use. */
-                uint32_t reserved:6;
+                uint32_t reserved:3;
             } PACKED;
         };
 
@@ -106,10 +109,34 @@ class ShadowPTE
         bool isDirty() const { return dirty; };
             /** Set dirty bit. */
         void setDirty(bool i_dirty) { dirty = i_dirty; };
+
             /** Get allocate-from-zero bit. */
         bool isAllocateFromZero() const { return allocate_from_zero; };
             /** Set allocate-from-zero bit. */
         void setAllocateFromZero(bool i_zero) { allocate_from_zero = i_zero; };
+
+            /** Get last_acces bits. */
+        uint8_t getLRU() const { return last_access; };
+            /** Increment the LRU bits. */
+        void incLRU() {
+	    if( last_access < 0b111 )
+	    {
+		last_access++;
+	    }
+	};
+            /** Decrement the LRU bits. */
+        void decLRU() {
+	    if( last_access > 0 )
+	    {
+		last_access--;
+	    }
+	};
+            /** Zero out the LRU bits. */
+        void zeroLRU() {
+	    last_access = 0;
+	};
+
+
 };
 
 #endif