mem: Add a wrapped DRAMSim2 memory controller

This patch adds DRAMSim2 as a memory controller by wrapping the
external library and creating a sublass of AbstractMemory that bridges
between the semantics of gem5 and the DRAMSim2 interface.

The DRAMSim2 wrapper extracts the clock period from the config
file. There is no way of extracting this information from DRAMSim2
itself, so we simply read the same config file and get it from there.

To properly model the response queue, the wrapper keeps track of how
many transactions are in the actual controller, and how many are
stacking up waiting to be sent back as responses (in the wrapper). The
latter requires us to move away from the queued port and manage the
packets ourselves. This is due to DRAMSim2 not having any flow control
on the response path.

DRAMSim2 assumes that the transactions it is given are matching the
burst size of the choosen memory. The wrapper checks to ensure the
cache line size of the system matches the burst size of DRAMSim2 as
there are currently no provisions to split the system requests. In
theory we could allow a cache line size smaller than the burst size,
but that would lead to inefficient use of the DRAM, so for not we
fatal also in this case.

1 files changed, 199 insertions, 0 deletions

diff --git a/src/mem/dramsim2_wrapper.cc b/src/mem/dramsim2_wrapper.cc
new file mode 100644
index 000000000..34a7ad5d5
--- /dev/null
+++ b/src/mem/dramsim2_wrapper.cc
@@ -0,0 +1,199 @@
+/*
+ * Copyright (c) 2013 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * 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: Andreas Hansson
+ */
+
+#include <cassert>
+
+/**
+ * When building the debug binary, we need to undo the command-line
+ * definition of DEBUG not to clash with DRAMSim2 print macros that
+ * are included for no obvious reason.
+ */
+#ifdef DEBUG
+#undef DEBUG
+#endif
+
+#include <fstream>
+
+#include "DRAMSim2/MultiChannelMemorySystem.h"
+#include "base/compiler.hh"
+#include "base/misc.hh"
+#include "mem/dramsim2_wrapper.hh"
+
+/**
+ * DRAMSim2 requires SHOW_SIM_OUTPUT to be defined (declared extern in
+ * the DRAMSim2 print macros), otherwise we get linking errors due to
+ * undefined references
+ */
+int SHOW_SIM_OUTPUT = 0;
+
+DRAMSim2Wrapper::DRAMSim2Wrapper(const std::string& config_file,
+                                 const std::string& system_file,
+                                 const std::string& working_dir,
+                                 const std::string& trace_file,
+                                 unsigned int memory_size_mb,
+                                 bool enable_debug) :
+    dramsim(new DRAMSim::MultiChannelMemorySystem(config_file, system_file,
+                                                  working_dir, trace_file,
+                                                  memory_size_mb, NULL, NULL)),
+    _clockPeriod(0.0), _queueSize(0), _burstSize(0)
+{
+    // tell DRAMSim2 to ignore its internal notion of a CPU frequency
+    dramsim->setCPUClockSpeed(0);
+
+    // switch on debug output if requested
+    if (enable_debug)
+        SHOW_SIM_OUTPUT = 1;
+
+    // there is no way of getting DRAMSim2 to tell us what frequency
+    // it is assuming, so we have to extract it ourselves
+    _clockPeriod = extractConfig<double>("tCK=",
+                                         working_dir + '/' + config_file);
+
+    if (!_clockPeriod)
+        fatal("DRAMSim2 wrapper failed to get clock\n");
+
+    // we also need to know what transaction queue size DRAMSim2 is
+    // using so we can stall when responses are blocked
+   _queueSize = extractConfig<unsigned int>("TRANS_QUEUE_DEPTH=",
+                                            working_dir + '/' + system_file);
+
+    if (!_queueSize)
+        fatal("DRAMSim2 wrapper failed to get queue size\n");
+
+
+   // finally, get the data bus bits and burst length so we can add a
+   // sanity check for the burst size
+    unsigned int dataBusBits =
+        extractConfig<unsigned int>("JEDEC_DATA_BUS_BITS=",
+                                    working_dir + '/' + system_file);
+   unsigned int burstLength =
+       extractConfig<unsigned int>("BL=", working_dir + '/' + config_file);
+
+   if (!dataBusBits || !burstLength)
+       fatal("DRAMSim22 wrapper failed to get burst size\n");
+
+   _burstSize = dataBusBits * burstLength / 8;
+}
+
+DRAMSim2Wrapper::~DRAMSim2Wrapper()
+{
+    delete dramsim;
+}
+
+template <typename T>
+T
+DRAMSim2Wrapper::extractConfig(const std::string& field_name,
+                               const std::string& file_name) const
+{
+    std::ifstream file_stream(file_name.c_str(), ios::in);
+
+    if (!file_stream.good())
+        fatal("DRAMSim2 wrapper could not open %s for reading\n", file_name);
+
+    bool found = false;
+    T res;
+    std::string line;
+    while (!found && file_stream) {
+        getline(file_stream, line);
+        if (line.substr(0, field_name.size()) == field_name) {
+            found = true;
+            istringstream iss(line.substr(field_name.size()));
+            iss >> res;
+        }
+    }
+
+    file_stream.close();
+
+    if (!found)
+        fatal("DRAMSim2 wrapper could not find %s in %s\n", field_name,
+              file_name);
+
+    return res;
+}
+
+void
+DRAMSim2Wrapper::printStats()
+{
+    dramsim->printStats(true);
+}
+
+void
+DRAMSim2Wrapper::setCallbacks(DRAMSim::TransactionCompleteCB* read_callback,
+                              DRAMSim::TransactionCompleteCB* write_callback)
+{
+    // simply pass it on, for now we ignore the power callback
+    dramsim->RegisterCallbacks(read_callback, write_callback, NULL);
+}
+
+bool
+DRAMSim2Wrapper::canAccept() const
+{
+    return dramsim->willAcceptTransaction();
+}
+
+void
+DRAMSim2Wrapper::enqueue(bool is_write, uint64_t addr)
+{
+    bool success M5_VAR_USED = dramsim->addTransaction(is_write, addr);
+    assert(success);
+}
+
+double
+DRAMSim2Wrapper::clockPeriod() const
+{
+    return _clockPeriod;
+}
+
+unsigned int
+DRAMSim2Wrapper::queueSize() const
+{
+    return _queueSize;
+}
+
+unsigned int
+DRAMSim2Wrapper::burstSize() const
+{
+    return _burstSize;
+}
+
+void
+DRAMSim2Wrapper::tick()
+{
+    dramsim->update();
+}