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/*
* 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.
*/
#ifndef __LEARNING_GEM5_SIMPLE_CACHE_SIMPLE_CACHE_HH__
#define __LEARNING_GEM5_SIMPLE_CACHE_SIMPLE_CACHE_HH__
#include <unordered_map>
#include "base/statistics.hh"
#include "mem/port.hh"
#include "params/SimpleCache.hh"
#include "sim/clocked_object.hh"
/**
* A very simple cache object. Has a fully-associative data store with random
* replacement.
* This cache is fully blocking (not non-blocking). Only a single request can
* be outstanding at a time.
* This cache is a writeback cache.
*/
class SimpleCache : public ClockedObject
{
private:
/**
* Port on the CPU-side that receives requests.
* Mostly just forwards requests to the cache (owner)
*/
class CPUSidePort : public ResponsePort
{
private:
/// Since this is a vector port, need to know what number this one is
int id;
/// The object that owns this object (SimpleCache)
SimpleCache *owner;
/// True if the port needs to send a retry req.
bool needRetry;
/// If we tried to send a packet and it was blocked, store it here
PacketPtr blockedPacket;
public:
/**
* Constructor. Just calls the superclass constructor.
*/
CPUSidePort(const std::string& name, int id, SimpleCache *owner) :
ResponsePort(name, owner), id(id), owner(owner), needRetry(false),
blockedPacket(nullptr)
{ }
/**
* Send a packet across this port. This is called by the owner and
* all of the flow control is hanled in this function.
* This is a convenience function for the SimpleCache to send pkts.
*
* @param packet to send.
*/
void sendPacket(PacketPtr pkt);
/**
* Get a list of the non-overlapping address ranges the owner is
* responsible for. All response ports must override this function
* and return a populated list with at least one item.
*
* @return a list of ranges responded to
*/
AddrRangeList getAddrRanges() const override;
/**
* Send a retry to the peer port only if it is needed. This is called
* from the SimpleCache whenever it is unblocked.
*/
void trySendRetry();
protected:
/**
* Receive an atomic request packet from the request port.
* No need to implement in this simple cache.
*/
Tick recvAtomic(PacketPtr pkt) override
{ panic("recvAtomic unimpl."); }
/**
* Receive a functional request packet from the request port.
* Performs a "debug" access updating/reading the data in place.
*
* @param packet the requestor sent.
*/
void recvFunctional(PacketPtr pkt) override;
/**
* Receive a timing request from the request port.
*
* @param the packet that the requestor sent
* @return whether this object can consume to packet. If false, we
* will call sendRetry() when we can try to receive this
* request again.
*/
bool recvTimingReq(PacketPtr pkt) override;
/**
* Called by the request port if sendTimingResp was called on this
* response port (causing recvTimingResp to be called on the request
* port) and was unsuccessful.
*/
void recvRespRetry() override;
};
/**
* Port on the memory-side that receives responses.
* Mostly just forwards requests to the cache (owner)
*/
class MemSidePort : public RequestPort
{
private:
/// The object that owns this object (SimpleCache)
SimpleCache *owner;
/// If we tried to send a packet and it was blocked, store it here
PacketPtr blockedPacket;
public:
/**
* Constructor. Just calls the superclass constructor.
*/
MemSidePort(const std::string& name, SimpleCache *owner) :
RequestPort(name, owner), owner(owner), blockedPacket(nullptr)
{ }
/**
* Send a packet across this port. This is called by the owner and
* all of the flow control is hanled in this function.
* This is a convenience function for the SimpleCache to send pkts.
*
* @param packet to send.
*/
void sendPacket(PacketPtr pkt);
protected:
/**
* Receive a timing response from the response port.
*/
bool recvTimingResp(PacketPtr pkt) override;
/**
* Called by the response port if sendTimingReq was called on this
* request port (causing recvTimingReq to be called on the response
* port) and was unsuccesful.
*/
void recvReqRetry() override;
/**
* Called to receive an address range change from the peer response
* port. The default implementation ignores the change and does
* nothing. Override this function in a derived class if the owner
* needs to be aware of the address ranges, e.g. in an
* interconnect component like a bus.
*/
void recvRangeChange() override;
};
/**
* Handle the request from the CPU side. Called from the CPU port
* on a timing request.
*
* @param requesting packet
* @param id of the port to send the response
* @return true if we can handle the request this cycle, false if the
* requestor needs to retry later
*/
bool handleRequest(PacketPtr pkt, int port_id);
/**
* Handle the respone from the memory side. Called from the memory port
* on a timing response.
*
* @param responding packet
* @return true if we can handle the response this cycle, false if the
* responder needs to retry later
*/
bool handleResponse(PacketPtr pkt);
/**
* Send the packet to the CPU side.
* This function assumes the pkt is already a response packet and forwards
* it to the correct port. This function also unblocks this object and
* cleans up the whole request.
*
* @param the packet to send to the cpu side
*/
void sendResponse(PacketPtr pkt);
/**
* Handle a packet functionally. Update the data on a write and get the
* data on a read. Called from CPU port on a recv functional.
*
* @param packet to functionally handle
*/
void handleFunctional(PacketPtr pkt);
/**
* Access the cache for a timing access. This is called after the cache
* access latency has already elapsed.
*/
void accessTiming(PacketPtr pkt);
/**
* This is where we actually update / read from the cache. This function
* is executed on both timing and functional accesses.
*
* @return true if a hit, false otherwise
*/
bool accessFunctional(PacketPtr pkt);
/**
* Insert a block into the cache. If there is no room left in the cache,
* then this function evicts a random entry t make room for the new block.
*
* @param packet with the data (and address) to insert into the cache
*/
void insert(PacketPtr pkt);
/**
* Return the address ranges this cache is responsible for. Just use the
* same as the next upper level of the hierarchy.
*
* @return the address ranges this cache is responsible for
*/
AddrRangeList getAddrRanges() const;
/**
* Tell the CPU side to ask for our memory ranges.
*/
void sendRangeChange() const;
/// Latency to check the cache. Number of cycles for both hit and miss
const Cycles latency;
/// The block size for the cache
const unsigned blockSize;
/// Number of blocks in the cache (size of cache / block size)
const unsigned capacity;
/// Instantiation of the CPU-side port
std::vector<CPUSidePort> cpuPorts;
/// Instantiation of the memory-side port
MemSidePort memPort;
/// True if this cache is currently blocked waiting for a response.
bool blocked;
/// Packet that we are currently handling. Used for upgrading to larger
/// cache line sizes
PacketPtr originalPacket;
/// The port to send the response when we recieve it back
int waitingPortId;
/// For tracking the miss latency
Tick missTime;
/// An incredibly simple cache storage. Maps block addresses to data
std::unordered_map<Addr, uint8_t*> cacheStore;
/// Cache statistics
protected:
struct SimpleCacheStats : public Stats::Group
{
SimpleCacheStats(Stats::Group *parent);
Stats::Scalar hits;
Stats::Scalar misses;
Stats::Histogram missLatency;
Stats::Formula hitRatio;
} stats;
public:
/** constructor
*/
SimpleCache(SimpleCacheParams *params);
/**
* Get a port with a given name and index. This is used at
* binding time and returns a reference to a protocol-agnostic
* port.
*
* @param if_name Port name
* @param idx Index in the case of a VectorPort
*
* @return A reference to the given port
*/
Port &getPort(const std::string &if_name,
PortID idx=InvalidPortID) override;
};
#endif // __LEARNING_GEM5_SIMPLE_CACHE_SIMPLE_CACHE_HH__