mem: refactor LRU cache tags and add random replacement tags

this patch implements a new tags class that uses a random replacement policy.
these tags prefer to evict invalid blocks first, if none are available a
replacement candidate is chosen at random.

this patch factors out the common code in the LRU class and creates a new
abstract class: the BaseSetAssoc class. any set associative tag class must
implement the functionality related to the actual replacement policy in the
following methods:

accessBlock()
findVictim()
insertBlock()
invalidate()

1 files changed, 68 insertions, 0 deletions

diff --git a/src/mem/cache/tags/random_repl.hh b/src/mem/cache/tags/random_repl.hh
new file mode 100644
index 000000000..7f2795379
--- /dev/null
+++ b/src/mem/cache/tags/random_repl.hh
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2014 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.
+ *
+ * Authors: Anthony Gutierrez
+ */
+
+/**
+ * @file
+ * Declaration of a random replacement tag store.
+ * The RandomRepl tags first try to evict an invalid
+ * block. If no invalid blocks are found, a candidate
+ * for eviction is found at random.
+ */
+
+#ifndef __MEM_CACHE_TAGS_RANDOM_REPL_HH__
+#define __MEM_CACHE_TAGS_RANDOM_REPL_HH__
+
+#include "mem/cache/tags/base_set_assoc.hh"
+#include "params/RandomRepl.hh"
+
+class RandomRepl : public BaseSetAssoc
+{
+  public:
+    /** Convenience typedef. */
+    typedef RandomReplParams Params;
+
+    /**
+     * Construct and initiliaze this tag store.
+     */
+    RandomRepl(const Params *p);
+
+    /**
+     * Destructor
+     */
+    ~RandomRepl() {}
+
+    BlkType* accessBlock(Addr addr, bool is_secure, Cycles &lat,
+                         int context_src);
+    BlkType* findVictim(Addr addr) const;
+    void insertBlock(PacketPtr pkt, BlkType *blk);
+    void invalidate(BlkType *blk);
+};
+
+#endif // __MEM_CACHE_TAGS_RANDOM_REPL_HH__