src/learning_gem5/part2/simple_cache.cc - public/gem5 - Git at Google

 /*
  * Copyright (c) 2017 Jason Lowe-Power
  * 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: Jason Lowe-Power
  */

 #include "learning_gem5/part2/simple_cache.hh"

 #include "base/random.hh"
 #include "debug/SimpleCache.hh"
 #include "sim/system.hh"

 SimpleCache::SimpleCache(SimpleCacheParams *params) :
     MemObject(params),
     latency(params->latency),
     blockSize(params->system->cacheLineSize()),
     capacity(params->size / blockSize),
     memPort(params->name + ".mem_side", this),
     blocked(false), originalPacket(nullptr), waitingPortId(-1)
 {
     // Since the CPU side ports are a vector of ports, create an instance of
     // the CPUSidePort for each connection. This member of params is
     // automatically created depending on the name of the vector port and
     // holds the number of connections to this port name
     for (int i = 0; i < params->port_cpu_side_connection_count; ++i) {
         cpuPorts.emplace_back(name() + csprintf(".cpu_side[%d]", i), i, this);
     }
 }

 BaseMasterPort&
 SimpleCache::getMasterPort(const std::string& if_name, PortID idx)
 {
     panic_if(idx != InvalidPortID, "This object doesn't support vector ports");

     // This is the name from the Python SimObject declaration in SimpleCache.py
     if (if_name == "mem_side") {
         return memPort;
     } else {
         // pass it along to our super class
         return MemObject::getMasterPort(if_name, idx);
     }
 }

 BaseSlavePort&
 SimpleCache::getSlavePort(const std::string& if_name, PortID idx)
 {
     // This is the name from the Python SimObject declaration (SimpleMemobj.py)
     if (if_name == "cpu_side" && idx < cpuPorts.size()) {
         // We should have already created all of the ports in the constructor
         return cpuPorts[idx];
     } else {
         // pass it along to our super class
         return MemObject::getSlavePort(if_name, idx);
     }
 }

 void
 SimpleCache::CPUSidePort::sendPacket(PacketPtr pkt)
 {
     // Note: This flow control is very simple since the cache is blocking.

     panic_if(blockedPacket != nullptr, "Should never try to send if blocked!");

     // If we can't send the packet across the port, store it for later.
     DPRINTF(SimpleCache, "Sending %s to CPU\n", pkt->print());
     if (!sendTimingResp(pkt)) {
         DPRINTF(SimpleCache, "failed!\n");
         blockedPacket = pkt;
     }
 }

 AddrRangeList
 SimpleCache::CPUSidePort::getAddrRanges() const
 {
     return owner->getAddrRanges();
 }

 void
 SimpleCache::CPUSidePort::trySendRetry()
 {
     if (needRetry && blockedPacket == nullptr) {
         // Only send a retry if the port is now completely free
         needRetry = false;
         DPRINTF(SimpleCache, "Sending retry req.\n");
         sendRetryReq();
     }
 }

 void
 SimpleCache::CPUSidePort::recvFunctional(PacketPtr pkt)
 {
     // Just forward to the cache.
     return owner->handleFunctional(pkt);
 }

 bool
 SimpleCache::CPUSidePort::recvTimingReq(PacketPtr pkt)
 {
     DPRINTF(SimpleCache, "Got request %s\n", pkt->print());

     if (blockedPacket || needRetry) {
         // The cache may not be able to send a reply if this is blocked
         DPRINTF(SimpleCache, "Request blocked\n");
         needRetry = true;
         return false;
     }
     // Just forward to the cache.
     if (!owner->handleRequest(pkt, id)) {
         DPRINTF(SimpleCache, "Request failed\n");
         // stalling
         needRetry = true;
         return false;
     } else {
         DPRINTF(SimpleCache, "Request succeeded\n");
         return true;
     }
 }

 void
 SimpleCache::CPUSidePort::recvRespRetry()
 {
     // We should have a blocked packet if this function is called.
     assert(blockedPacket != nullptr);

     // Grab the blocked packet.
     PacketPtr pkt = blockedPacket;
     blockedPacket = nullptr;

     DPRINTF(SimpleCache, "Retrying response pkt %s\n", pkt->print());
     // Try to resend it. It's possible that it fails again.
     sendPacket(pkt);

     // We may now be able to accept new packets
     trySendRetry();
 }

 void
 SimpleCache::MemSidePort::sendPacket(PacketPtr pkt)
 {
     // Note: This flow control is very simple since the cache is blocking.

     panic_if(blockedPacket != nullptr, "Should never try to send if blocked!");

     // If we can't send the packet across the port, store it for later.
     if (!sendTimingReq(pkt)) {
         blockedPacket = pkt;
     }
 }

 bool
 SimpleCache::MemSidePort::recvTimingResp(PacketPtr pkt)
 {
     // Just forward to the cache.
     return owner->handleResponse(pkt);
 }

 void
 SimpleCache::MemSidePort::recvReqRetry()
 {
     // We should have a blocked packet if this function is called.
     assert(blockedPacket != nullptr);

     // Grab the blocked packet.
     PacketPtr pkt = blockedPacket;
     blockedPacket = nullptr;

     // Try to resend it. It's possible that it fails again.
     sendPacket(pkt);
 }

 void
 SimpleCache::MemSidePort::recvRangeChange()
 {
     owner->sendRangeChange();
 }

 bool
 SimpleCache::handleRequest(PacketPtr pkt, int port_id)
 {
     if (blocked) {
         // There is currently an outstanding request so we can't respond. Stall
         return false;
     }

     DPRINTF(SimpleCache, "Got request for addr %#x\n", pkt->getAddr());

     // This cache is now blocked waiting for the response to this packet.
     blocked = true;

     // Store the port for when we get the response
     assert(waitingPortId == -1);
     waitingPortId = port_id;

     // Schedule an event after cache access latency to actually access
     schedule(new EventFunctionWrapper([this, pkt]{ accessTiming(pkt); },
                                       name() + ".accessEvent", true),
              clockEdge(latency));

     return true;
 }

 bool
 SimpleCache::handleResponse(PacketPtr pkt)
 {
     assert(blocked);
     DPRINTF(SimpleCache, "Got response for addr %#x\n", pkt->getAddr());

     // For now assume that inserts are off of the critical path and don't count
     // for any added latency.
     insert(pkt);

     missLatency.sample(curTick() - missTime);

     // If we had to upgrade the request packet to a full cache line, now we
     // can use that packet to construct the response.
     if (originalPacket != nullptr) {
         DPRINTF(SimpleCache, "Copying data from new packet to old\n");
         // We had to upgrade a previous packet. We can functionally deal with
         // the cache access now. It better be a hit.
         bool hit M5_VAR_USED = accessFunctional(originalPacket);
         panic_if(!hit, "Should always hit after inserting");
         originalPacket->makeResponse();
         delete pkt; // We may need to delay this, I'm not sure.
         pkt = originalPacket;
         originalPacket = nullptr;
     } // else, pkt contains the data it needs

     sendResponse(pkt);

     return true;
 }

 void SimpleCache::sendResponse(PacketPtr pkt)
 {
     assert(blocked);
     DPRINTF(SimpleCache, "Sending resp for addr %#x\n", pkt->getAddr());

     int port = waitingPortId;

     // The packet is now done. We're about to put it in the port, no need for
     // this object to continue to stall.
     // We need to free the resource before sending the packet in case the CPU
     // tries to send another request immediately (e.g., in the same callchain).
     blocked = false;
     waitingPortId = -1;

     // Simply forward to the memory port
     cpuPorts[port].sendPacket(pkt);

     // For each of the cpu ports, if it needs to send a retry, it should do it
     // now since this memory object may be unblocked now.
     for (auto& port : cpuPorts) {
         port.trySendRetry();
     }
 }

 void
 SimpleCache::handleFunctional(PacketPtr pkt)
 {
     if (accessFunctional(pkt)) {
         pkt->makeResponse();
     } else {
         memPort.sendFunctional(pkt);
     }
 }

 void
 SimpleCache::accessTiming(PacketPtr pkt)
 {
     bool hit = accessFunctional(pkt);

     DPRINTF(SimpleCache, "%s for packet: %s\n", hit ? "Hit" : "Miss",
             pkt->print());

     if (hit) {
         // Respond to the CPU side
         hits++; // update stats
         DDUMP(SimpleCache, pkt->getConstPtr<uint8_t>(), pkt->getSize());
         pkt->makeResponse();
         sendResponse(pkt);
     } else {
         misses++; // update stats
         missTime = curTick();
         // Forward to the memory side.
         // We can't directly forward the packet unless it is exactly the size
         // of the cache line, and aligned. Check for that here.
         Addr addr = pkt->getAddr();
         Addr block_addr = pkt->getBlockAddr(blockSize);
         unsigned size = pkt->getSize();
         if (addr == block_addr && size == blockSize) {
             // Aligned and block size. We can just forward.
             DPRINTF(SimpleCache, "forwarding packet\n");
             memPort.sendPacket(pkt);
         } else {
             DPRINTF(SimpleCache, "Upgrading packet to block size\n");
             panic_if(addr - block_addr + size > blockSize,
                      "Cannot handle accesses that span multiple cache lines");
             // Unaligned access to one cache block
             assert(pkt->needsResponse());
             MemCmd cmd;
             if (pkt->isWrite() || pkt->isRead()) {
                 // Read the data from memory to write into the block.
                 // We'll write the data in the cache (i.e., a writeback cache)
                 cmd = MemCmd::ReadReq;
             } else {
                 panic("Unknown packet type in upgrade size");
             }

             // Create a new packet that is blockSize
             PacketPtr new_pkt = new Packet(pkt->req, cmd, blockSize);
             new_pkt->allocate();

             // Should now be block aligned
             assert(new_pkt->getAddr() == new_pkt->getBlockAddr(blockSize));

             // Save the old packet
             originalPacket = pkt;

             DPRINTF(SimpleCache, "forwarding packet\n");
             memPort.sendPacket(new_pkt);
         }
     }
 }

 bool
 SimpleCache::accessFunctional(PacketPtr pkt)
 {
     Addr block_addr = pkt->getBlockAddr(blockSize);
     auto it = cacheStore.find(block_addr);
     if (it != cacheStore.end()) {
         if (pkt->isWrite()) {
             // Write the data into the block in the cache
             pkt->writeDataToBlock(it->second, blockSize);
         } else if (pkt->isRead()) {
             // Read the data out of the cache block into the packet
             pkt->setDataFromBlock(it->second, blockSize);
         } else {
             panic("Unknown packet type!");
         }
         return true;
     }
     return false;
 }

 void
 SimpleCache::insert(PacketPtr pkt)
 {
     // The packet should be aligned.
     assert(pkt->getAddr() ==  pkt->getBlockAddr(blockSize));
     // The address should not be in the cache
     assert(cacheStore.find(pkt->getAddr()) == cacheStore.end());
     // The pkt should be a response
     assert(pkt->isResponse());

     if (cacheStore.size() >= capacity) {
         // Select random thing to evict. This is a little convoluted since we
         // are using a std::unordered_map. See http://bit.ly/2hrnLP2
         int bucket, bucket_size;
         do {
             bucket = random_mt.random(0, (int)cacheStore.bucket_count() - 1);
         } while ( (bucket_size = cacheStore.bucket_size(bucket)) == 0 );
         auto block = std::next(cacheStore.begin(bucket),
                                random_mt.random(0, bucket_size - 1));

         DPRINTF(SimpleCache, "Removing addr %#x\n", block->first);

         // Write back the data.
         // Create a new request-packet pair
         RequestPtr req = std::make_shared<Request>(
             block->first, blockSize, 0, 0);

         PacketPtr new_pkt = new Packet(req, MemCmd::WritebackDirty, blockSize);
         new_pkt->dataDynamic(block->second); // This will be deleted later

         DPRINTF(SimpleCache, "Writing packet back %s\n", pkt->print());
         // Send the write to memory
         memPort.sendPacket(new_pkt);

         // Delete this entry
         cacheStore.erase(block->first);
     }

     DPRINTF(SimpleCache, "Inserting %s\n", pkt->print());
     DDUMP(SimpleCache, pkt->getConstPtr<uint8_t>(), blockSize);

     // Allocate space for the cache block data
     uint8_t *data = new uint8_t[blockSize];

     // Insert the data and address into the cache store
     cacheStore[pkt->getAddr()] = data;

     // Write the data into the cache
     pkt->writeDataToBlock(data, blockSize);
 }

 AddrRangeList
 SimpleCache::getAddrRanges() const
 {
     DPRINTF(SimpleCache, "Sending new ranges\n");
     // Just use the same ranges as whatever is on the memory side.
     return memPort.getAddrRanges();
 }

 void
 SimpleCache::sendRangeChange() const
 {
     for (auto& port : cpuPorts) {
         port.sendRangeChange();
     }
 }

 void
 SimpleCache::regStats()
 {
     // If you don't do this you get errors about uninitialized stats.
     MemObject::regStats();

     hits.name(name() + ".hits")
         .desc("Number of hits")
         ;

     misses.name(name() + ".misses")
         .desc("Number of misses")
         ;

     missLatency.name(name() + ".missLatency")
         .desc("Ticks for misses to the cache")
         .init(16) // number of buckets
         ;

     hitRatio.name(name() + ".hitRatio")
         .desc("The ratio of hits to the total accesses to the cache")
         ;

     hitRatio = hits / (hits + misses);

 }


 SimpleCache*
 SimpleCacheParams::create()
 {
     return new SimpleCache(this);
 }
	/*
	* Copyright (c) 2017 Jason Lowe-Power
	* 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: Jason Lowe-Power
	*/

	#include "learning_gem5/part2/simple_cache.hh"

	#include "base/random.hh"
	#include "debug/SimpleCache.hh"
	#include "sim/system.hh"

	SimpleCache::SimpleCache(SimpleCacheParams *params) :
	MemObject(params),
	latency(params->latency),
	blockSize(params->system->cacheLineSize()),
	capacity(params->size / blockSize),
	memPort(params->name + ".mem_side", this),
	blocked(false), originalPacket(nullptr), waitingPortId(-1)
	{
	// Since the CPU side ports are a vector of ports, create an instance of
	// the CPUSidePort for each connection. This member of params is
	// automatically created depending on the name of the vector port and
	// holds the number of connections to this port name
	for (int i = 0; i < params->port_cpu_side_connection_count; ++i) {
	cpuPorts.emplace_back(name() + csprintf(".cpu_side[%d]", i), i, this);
	}
	}

	BaseMasterPort&
	SimpleCache::getMasterPort(const std::string& if_name, PortID idx)
	{
	panic_if(idx != InvalidPortID, "This object doesn't support vector ports");

	// This is the name from the Python SimObject declaration in SimpleCache.py
	if (if_name == "mem_side") {
	return memPort;
	} else {
	// pass it along to our super class
	return MemObject::getMasterPort(if_name, idx);
	}
	}

	BaseSlavePort&
	SimpleCache::getSlavePort(const std::string& if_name, PortID idx)
	{
	// This is the name from the Python SimObject declaration (SimpleMemobj.py)
	if (if_name == "cpu_side" && idx < cpuPorts.size()) {
	// We should have already created all of the ports in the constructor
	return cpuPorts[idx];
	} else {
	// pass it along to our super class
	return MemObject::getSlavePort(if_name, idx);
	}
	}

	void
	SimpleCache::CPUSidePort::sendPacket(PacketPtr pkt)
	{
	// Note: This flow control is very simple since the cache is blocking.

	panic_if(blockedPacket != nullptr, "Should never try to send if blocked!");

	// If we can't send the packet across the port, store it for later.
	DPRINTF(SimpleCache, "Sending %s to CPU\n", pkt->print());
	if (!sendTimingResp(pkt)) {
	DPRINTF(SimpleCache, "failed!\n");
	blockedPacket = pkt;
	}
	}

	AddrRangeList
	SimpleCache::CPUSidePort::getAddrRanges() const
	{
	return owner->getAddrRanges();
	}

	void
	SimpleCache::CPUSidePort::trySendRetry()
	{
	if (needRetry && blockedPacket == nullptr) {
	// Only send a retry if the port is now completely free
	needRetry = false;
	DPRINTF(SimpleCache, "Sending retry req.\n");
	sendRetryReq();
	}
	}

	void
	SimpleCache::CPUSidePort::recvFunctional(PacketPtr pkt)
	{
	// Just forward to the cache.
	return owner->handleFunctional(pkt);
	}

	bool
	SimpleCache::CPUSidePort::recvTimingReq(PacketPtr pkt)
	{
	DPRINTF(SimpleCache, "Got request %s\n", pkt->print());

	if (blockedPacket \|\| needRetry) {
	// The cache may not be able to send a reply if this is blocked
	DPRINTF(SimpleCache, "Request blocked\n");
	needRetry = true;
	return false;
	}
	// Just forward to the cache.
	if (!owner->handleRequest(pkt, id)) {
	DPRINTF(SimpleCache, "Request failed\n");
	// stalling
	needRetry = true;
	return false;
	} else {
	DPRINTF(SimpleCache, "Request succeeded\n");
	return true;
	}
	}

	void
	SimpleCache::CPUSidePort::recvRespRetry()
	{
	// We should have a blocked packet if this function is called.
	assert(blockedPacket != nullptr);

	// Grab the blocked packet.
	PacketPtr pkt = blockedPacket;
	blockedPacket = nullptr;

	DPRINTF(SimpleCache, "Retrying response pkt %s\n", pkt->print());
	// Try to resend it. It's possible that it fails again.
	sendPacket(pkt);

	// We may now be able to accept new packets
	trySendRetry();
	}

	void
	SimpleCache::MemSidePort::sendPacket(PacketPtr pkt)
	{
	// Note: This flow control is very simple since the cache is blocking.

	panic_if(blockedPacket != nullptr, "Should never try to send if blocked!");

	// If we can't send the packet across the port, store it for later.
	if (!sendTimingReq(pkt)) {
	blockedPacket = pkt;
	}
	}

	bool
	SimpleCache::MemSidePort::recvTimingResp(PacketPtr pkt)
	{
	// Just forward to the cache.
	return owner->handleResponse(pkt);
	}

	void
	SimpleCache::MemSidePort::recvReqRetry()
	{
	// We should have a blocked packet if this function is called.
	assert(blockedPacket != nullptr);

	// Grab the blocked packet.
	PacketPtr pkt = blockedPacket;
	blockedPacket = nullptr;

	// Try to resend it. It's possible that it fails again.
	sendPacket(pkt);
	}

	void
	SimpleCache::MemSidePort::recvRangeChange()
	{
	owner->sendRangeChange();
	}

	bool
	SimpleCache::handleRequest(PacketPtr pkt, int port_id)
	{
	if (blocked) {
	// There is currently an outstanding request so we can't respond. Stall
	return false;
	}

	DPRINTF(SimpleCache, "Got request for addr %#x\n", pkt->getAddr());

	// This cache is now blocked waiting for the response to this packet.
	blocked = true;

	// Store the port for when we get the response
	assert(waitingPortId == -1);
	waitingPortId = port_id;

	// Schedule an event after cache access latency to actually access
	schedule(new EventFunctionWrapper([this, pkt]{ accessTiming(pkt); },
	name() + ".accessEvent", true),
	clockEdge(latency));

	return true;
	}

	bool
	SimpleCache::handleResponse(PacketPtr pkt)
	{
	assert(blocked);
	DPRINTF(SimpleCache, "Got response for addr %#x\n", pkt->getAddr());

	// For now assume that inserts are off of the critical path and don't count
	// for any added latency.
	insert(pkt);

	missLatency.sample(curTick() - missTime);

	// If we had to upgrade the request packet to a full cache line, now we
	// can use that packet to construct the response.
	if (originalPacket != nullptr) {
	DPRINTF(SimpleCache, "Copying data from new packet to old\n");
	// We had to upgrade a previous packet. We can functionally deal with
	// the cache access now. It better be a hit.
	bool hit M5_VAR_USED = accessFunctional(originalPacket);
	panic_if(!hit, "Should always hit after inserting");
	originalPacket->makeResponse();
	delete pkt; // We may need to delay this, I'm not sure.
	pkt = originalPacket;
	originalPacket = nullptr;
	} // else, pkt contains the data it needs

	sendResponse(pkt);

	return true;
	}

	void SimpleCache::sendResponse(PacketPtr pkt)
	{
	assert(blocked);
	DPRINTF(SimpleCache, "Sending resp for addr %#x\n", pkt->getAddr());

	int port = waitingPortId;

	// The packet is now done. We're about to put it in the port, no need for
	// this object to continue to stall.
	// We need to free the resource before sending the packet in case the CPU
	// tries to send another request immediately (e.g., in the same callchain).
	blocked = false;
	waitingPortId = -1;

	// Simply forward to the memory port
	cpuPorts[port].sendPacket(pkt);

	// For each of the cpu ports, if it needs to send a retry, it should do it
	// now since this memory object may be unblocked now.
	for (auto& port : cpuPorts) {
	port.trySendRetry();
	}
	}

	void
	SimpleCache::handleFunctional(PacketPtr pkt)
	{
	if (accessFunctional(pkt)) {
	pkt->makeResponse();
	} else {
	memPort.sendFunctional(pkt);
	}
	}

	void
	SimpleCache::accessTiming(PacketPtr pkt)
	{
	bool hit = accessFunctional(pkt);

	DPRINTF(SimpleCache, "%s for packet: %s\n", hit ? "Hit" : "Miss",
	pkt->print());

	if (hit) {
	// Respond to the CPU side
	hits++; // update stats
	DDUMP(SimpleCache, pkt->getConstPtr<uint8_t>(), pkt->getSize());
	pkt->makeResponse();
	sendResponse(pkt);
	} else {
	misses++; // update stats
	missTime = curTick();
	// Forward to the memory side.
	// We can't directly forward the packet unless it is exactly the size
	// of the cache line, and aligned. Check for that here.
	Addr addr = pkt->getAddr();
	Addr block_addr = pkt->getBlockAddr(blockSize);
	unsigned size = pkt->getSize();
	if (addr == block_addr && size == blockSize) {
	// Aligned and block size. We can just forward.
	DPRINTF(SimpleCache, "forwarding packet\n");
	memPort.sendPacket(pkt);
	} else {
	DPRINTF(SimpleCache, "Upgrading packet to block size\n");
	panic_if(addr - block_addr + size > blockSize,
	"Cannot handle accesses that span multiple cache lines");
	// Unaligned access to one cache block
	assert(pkt->needsResponse());
	MemCmd cmd;
	if (pkt->isWrite() \|\| pkt->isRead()) {
	// Read the data from memory to write into the block.
	// We'll write the data in the cache (i.e., a writeback cache)
	cmd = MemCmd::ReadReq;
	} else {
	panic("Unknown packet type in upgrade size");
	}

	// Create a new packet that is blockSize
	PacketPtr new_pkt = new Packet(pkt->req, cmd, blockSize);
	new_pkt->allocate();

	// Should now be block aligned
	assert(new_pkt->getAddr() == new_pkt->getBlockAddr(blockSize));

	// Save the old packet
	originalPacket = pkt;

	DPRINTF(SimpleCache, "forwarding packet\n");
	memPort.sendPacket(new_pkt);
	}
	}
	}

	bool
	SimpleCache::accessFunctional(PacketPtr pkt)
	{
	Addr block_addr = pkt->getBlockAddr(blockSize);
	auto it = cacheStore.find(block_addr);
	if (it != cacheStore.end()) {
	if (pkt->isWrite()) {
	// Write the data into the block in the cache
	pkt->writeDataToBlock(it->second, blockSize);
	} else if (pkt->isRead()) {
	// Read the data out of the cache block into the packet
	pkt->setDataFromBlock(it->second, blockSize);
	} else {
	panic("Unknown packet type!");
	}
	return true;
	}
	return false;
	}

	void
	SimpleCache::insert(PacketPtr pkt)
	{
	// The packet should be aligned.
	assert(pkt->getAddr() == pkt->getBlockAddr(blockSize));
	// The address should not be in the cache
	assert(cacheStore.find(pkt->getAddr()) == cacheStore.end());
	// The pkt should be a response
	assert(pkt->isResponse());

	if (cacheStore.size() >= capacity) {
	// Select random thing to evict. This is a little convoluted since we
	// are using a std::unordered_map. See http://bit.ly/2hrnLP2
	int bucket, bucket_size;
	do {
	bucket = random_mt.random(0, (int)cacheStore.bucket_count() - 1);
	} while ( (bucket_size = cacheStore.bucket_size(bucket)) == 0 );
	auto block = std::next(cacheStore.begin(bucket),
	random_mt.random(0, bucket_size - 1));

	DPRINTF(SimpleCache, "Removing addr %#x\n", block->first);

	// Write back the data.
	// Create a new request-packet pair
	RequestPtr req = std::make_shared<Request>(
	block->first, blockSize, 0, 0);

	PacketPtr new_pkt = new Packet(req, MemCmd::WritebackDirty, blockSize);
	new_pkt->dataDynamic(block->second); // This will be deleted later

	DPRINTF(SimpleCache, "Writing packet back %s\n", pkt->print());
	// Send the write to memory
	memPort.sendPacket(new_pkt);

	// Delete this entry
	cacheStore.erase(block->first);
	}

	DPRINTF(SimpleCache, "Inserting %s\n", pkt->print());
	DDUMP(SimpleCache, pkt->getConstPtr<uint8_t>(), blockSize);

	// Allocate space for the cache block data
	uint8_t *data = new uint8_t[blockSize];

	// Insert the data and address into the cache store
	cacheStore[pkt->getAddr()] = data;

	// Write the data into the cache
	pkt->writeDataToBlock(data, blockSize);
	}

	AddrRangeList
	SimpleCache::getAddrRanges() const
	{
	DPRINTF(SimpleCache, "Sending new ranges\n");
	// Just use the same ranges as whatever is on the memory side.
	return memPort.getAddrRanges();
	}

	void
	SimpleCache::sendRangeChange() const
	{
	for (auto& port : cpuPorts) {
	port.sendRangeChange();
	}
	}

	void
	SimpleCache::regStats()
	{
	// If you don't do this you get errors about uninitialized stats.
	MemObject::regStats();

	hits.name(name() + ".hits")
	.desc("Number of hits")
	;

	misses.name(name() + ".misses")
	.desc("Number of misses")
	;

	missLatency.name(name() + ".missLatency")
	.desc("Ticks for misses to the cache")
	.init(16) // number of buckets
	;

	hitRatio.name(name() + ".hitRatio")
	.desc("The ratio of hits to the total accesses to the cache")
	;

	hitRatio = hits / (hits + misses);

	}


	SimpleCache*
	SimpleCacheParams::create()
	{
	return new SimpleCache(this);
	}