base.hh

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/*
 * Copyright (c) 2012-2013, 2015-2016, 2018-2019, 2023-2024 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.
 *
 * Copyright (c) 2003-2005 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
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 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
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 *
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 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 */
 
#ifndef __MEM_CACHE_BASE_HH__
#define __MEM_CACHE_BASE_HH__
 
#include <cassert>
#include <cstdint>
#include <string>
 
#include "base/addr_range.hh"
#include "base/compiler.hh"
#include "base/statistics.hh"
#include "base/trace.hh"
#include "base/types.hh"
#include "debug/Cache.hh"
#include "debug/CachePort.hh"
#include "enums/Clusivity.hh"
#include "mem/cache/cache_blk.hh"
#include "mem/cache/cache_probe_arg.hh"
#include "mem/cache/compressors/base.hh"
#include "mem/cache/mshr_queue.hh"
#include "mem/cache/tags/base.hh"
#include "mem/cache/write_queue.hh"
#include "mem/cache/write_queue_entry.hh"
#include "mem/packet.hh"
#include "mem/packet_queue.hh"
#include "mem/qport.hh"
#include "mem/request.hh"
#include "params/WriteAllocator.hh"
#include "sim/clocked_object.hh"
#include "sim/eventq.hh"
#include "sim/probe/probe.hh"
#include "sim/serialize.hh"
#include "sim/sim_exit.hh"
#include "sim/system.hh"
 
namespace gem5
{
 
namespace prefetch
{
    class Base;
}
namespace partitioning_policy
{
    class PartitionManager;
}
class MSHR;
class RequestPort;
class QueueEntry;
struct BaseCacheParams;
 
class BaseCache : public ClockedObject
{
  protected:
    enum MSHRQueueIndex
    {
        MSHRQueue_MSHRs,
        MSHRQueue_WriteBuffer
    };
 
  public:
    enum BlockedCause
    {
        Blocked_NoMSHRs = MSHRQueue_MSHRs,
        Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
        Blocked_NoTargets,
        NUM_BLOCKED_CAUSES
    };
 
  protected:
 
    class CacheRequestPort : public QueuedRequestPort
    {
 
      public:
 
        void schedSendEvent(Tick time)
        {
            DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
            reqQueue.schedSendEvent(time);
        }
 
      protected:
 
        CacheRequestPort(const std::string &_name,
                        ReqPacketQueue &_reqQueue,
                        SnoopRespPacketQueue &_snoopRespQueue) :
            QueuedRequestPort(_name, _reqQueue, _snoopRespQueue)
        { }
 
        virtual bool isSnooping() const { return true; }
    };
 
    class CacheReqPacketQueue : public ReqPacketQueue
    {
 
      protected:
 
        BaseCache &cache;
        SnoopRespPacketQueue &snoopRespQueue;
 
      public:
 
        CacheReqPacketQueue(BaseCache &cache, RequestPort &port,
                            SnoopRespPacketQueue &snoop_resp_queue,
                            const std::string &label) :
            ReqPacketQueue(cache, port, label), cache(cache),
            snoopRespQueue(snoop_resp_queue) { }
 
        virtual void sendDeferredPacket();
 
        bool checkConflictingSnoop(const PacketPtr pkt)
        {
            if (snoopRespQueue.checkConflict(pkt, cache.blkSize)) {
                DPRINTF(CachePort, "Waiting for snoop response to be "
                        "sent\n");
                Tick when = snoopRespQueue.deferredPacketReadyTime();
                schedSendEvent(when);
                return true;
            }
            return false;
        }
    };
 
 
    class MemSidePort : public CacheRequestPort
    {
      private:
 
        CacheReqPacketQueue _reqQueue;
 
        SnoopRespPacketQueue _snoopRespQueue;
 
        // a pointer to our specific cache implementation
        BaseCache *cache;
 
      protected:
 
        virtual void recvTimingSnoopReq(PacketPtr pkt);
 
        virtual bool recvTimingResp(PacketPtr pkt);
 
        virtual Tick recvAtomicSnoop(PacketPtr pkt);
 
        virtual void recvFunctionalSnoop(PacketPtr pkt);
 
      public:
 
        MemSidePort(const std::string &_name, BaseCache *_cache,
                    const std::string &_label);
    };
 
    class CacheResponsePort : public QueuedResponsePort
    {
 
      public:
 
        void setBlocked();
 
        void clearBlocked();
 
        bool isBlocked() const { return blocked; }
 
      protected:
 
        CacheResponsePort(const std::string &_name, BaseCache& _cache,
                       const std::string &_label);
 
        BaseCache& cache;
 
        RespPacketQueue queue;
 
        bool blocked;
 
        bool mustSendRetry;
 
      private:
 
        void processSendRetry();
 
        EventFunctionWrapper sendRetryEvent;
 
    };
 
    class CpuSidePort : public CacheResponsePort
    {
      protected:
        virtual bool recvTimingSnoopResp(PacketPtr pkt) override;
 
        virtual bool tryTiming(PacketPtr pkt) override;
 
        virtual bool recvTimingReq(PacketPtr pkt) override;
 
        virtual Tick recvAtomic(PacketPtr pkt) override;
 
        virtual void recvFunctional(PacketPtr pkt) override;
 
        virtual AddrRangeList getAddrRanges() const override;
 
      public:
 
        CpuSidePort(const std::string &_name, BaseCache& _cache,
                    const std::string &_label);
 
    };
 
    CpuSidePort cpuSidePort;
    MemSidePort memSidePort;
 
  protected:
 
    struct CacheAccessorImpl : CacheAccessor
    {
        BaseCache &cache;
 
        CacheAccessorImpl(BaseCache &_cache) :cache(_cache) {}
 
        bool inCache(Addr addr, bool is_secure) const override
        { return cache.inCache(addr, is_secure); }
 
        bool hasBeenPrefetched(Addr addr, bool is_secure) const override
        { return cache.hasBeenPrefetched(addr, is_secure); }
 
        bool hasBeenPrefetched(Addr addr, bool is_secure,
                               RequestorID requestor) const override
        { return cache.hasBeenPrefetched(addr, is_secure, requestor); }
 
        bool inMissQueue(Addr addr, bool is_secure) const override
        { return cache.inMissQueue(addr, is_secure); }
 
        bool coalesce() const override
        { return cache.coalesce(); }
 
    } accessor;
 
    MSHRQueue mshrQueue;
 
    WriteQueue writeBuffer;
 
    BaseTags *tags;
 
    compression::Base* compressor;
 
    partitioning_policy::PartitionManager* partitionManager;
 
    prefetch::Base *prefetcher;
 
    ProbePointArg<CacheAccessProbeArg> *ppHit;
 
    ProbePointArg<CacheAccessProbeArg> *ppMiss;
 
    ProbePointArg<CacheAccessProbeArg> *ppFill;
 
    ProbePointArg<CacheDataUpdateProbeArg> *ppDataUpdate;
 
    WriteAllocator * const writeAllocator;
 
    TempCacheBlk *tempBlock;
 
    std::unique_ptr<Packet> pendingDelete;
 
    void markInService(MSHR *mshr, bool pending_modified_resp)
    {
        bool wasFull = mshrQueue.isFull();
        mshrQueue.markInService(mshr, pending_modified_resp);
 
        if (wasFull && !mshrQueue.isFull()) {
            clearBlocked(Blocked_NoMSHRs);
        }
    }
 
    void markInService(WriteQueueEntry *entry)
    {
        bool wasFull = writeBuffer.isFull();
        writeBuffer.markInService(entry);
 
        if (wasFull && !writeBuffer.isFull()) {
            clearBlocked(Blocked_NoWBBuffers);
        }
    }
 
    inline bool allocOnFill(MemCmd cmd) const
    {
        return clusivity == enums::mostly_incl ||
            cmd == MemCmd::WriteLineReq ||
            cmd == MemCmd::ReadReq ||
            cmd == MemCmd::WriteReq ||
            cmd.isPrefetch() ||
            cmd.isLLSC();
    }
 
    Addr regenerateBlkAddr(CacheBlk* blk);
 
    Cycles calculateTagOnlyLatency(const uint32_t delay,
                                   const Cycles lookup_lat) const;
    Cycles calculateAccessLatency(const CacheBlk* blk, const uint32_t delay,
                                  const Cycles lookup_lat) const;
 
    virtual bool access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
                        PacketList &writebacks);
 
    /*
     * Handle a timing request that hit in the cache
     *
     * @param ptk The request packet
     * @param blk The referenced block
     * @param request_time The tick at which the block lookup is compete
     */
    virtual void handleTimingReqHit(PacketPtr pkt, CacheBlk *blk,
                                    Tick request_time);
 
    /*
     * Handle a timing request that missed in the cache
     *
     * Implementation specific handling for different cache
     * implementations
     *
     * @param ptk The request packet
     * @param blk The referenced block
     * @param forward_time The tick at which we can process dependent requests
     * @param request_time The tick at which the block lookup is compete
     */
    virtual void handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk,
                                     Tick forward_time,
                                     Tick request_time) = 0;
 
    /*
     * Handle a timing request that missed in the cache
     *
     * Common functionality across different cache implementations
     *
     * @param ptk The request packet
     * @param blk The referenced block
     * @param mshr Any existing mshr for the referenced cache block
     * @param forward_time The tick at which we can process dependent requests
     * @param request_time The tick at which the block lookup is compete
     */
    void handleTimingReqMiss(PacketPtr pkt, MSHR *mshr, CacheBlk *blk,
                             Tick forward_time, Tick request_time);
 
    virtual void recvTimingReq(PacketPtr pkt);
 
    void handleUncacheableWriteResp(PacketPtr pkt);
 
    virtual void serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt,
                                    CacheBlk *blk) = 0;
 
    virtual void recvTimingResp(PacketPtr pkt);
 
    virtual void recvTimingSnoopReq(PacketPtr pkt) = 0;
 
    virtual void recvTimingSnoopResp(PacketPtr pkt) = 0;
 
    virtual Cycles handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
                                       PacketList &writebacks) = 0;
 
    virtual Tick recvAtomic(PacketPtr pkt);
 
    virtual Tick recvAtomicSnoop(PacketPtr pkt) = 0;
 
    virtual void functionalAccess(PacketPtr pkt, bool from_cpu_side);
 
    void updateBlockData(CacheBlk *blk, const PacketPtr cpkt,
        bool has_old_data);
 
    void cmpAndSwap(CacheBlk *blk, PacketPtr pkt);
 
    QueueEntry* getNextQueueEntry();
 
    virtual void doWritebacks(PacketList& writebacks, Tick forward_time) = 0;
 
    virtual void doWritebacksAtomic(PacketList& writebacks) = 0;
 
    virtual PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
                                       bool needs_writable,
                                       bool is_whole_line_write) const = 0;
 
    const bool writebackClean;
 
    PacketPtr tempBlockWriteback;
 
    void writebackTempBlockAtomic() {
        assert(tempBlockWriteback != nullptr);
        PacketList writebacks{tempBlockWriteback};
        doWritebacksAtomic(writebacks);
        tempBlockWriteback = nullptr;
    }
 
    EventFunctionWrapper writebackTempBlockAtomicEvent;
 
    bool updateCompressionData(CacheBlk *&blk, const uint64_t* data,
                               PacketList &writebacks);
 
    virtual void satisfyRequest(PacketPtr pkt, CacheBlk *blk,
                                bool deferred_response = false,
                                bool pending_downgrade = false);
 
    void maintainClusivity(bool from_cache, CacheBlk *blk);
 
    bool handleEvictions(std::vector<CacheBlk*> &evict_blks,
        PacketList &writebacks);
 
    CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk,
                         PacketList &writebacks, bool allocate);
 
    CacheBlk *allocateBlock(const PacketPtr pkt, PacketList &writebacks);
    [[nodiscard]] virtual PacketPtr evictBlock(CacheBlk *blk) = 0;
 
    void evictBlock(CacheBlk *blk, PacketList &writebacks);
 
    void invalidateBlock(CacheBlk *blk);
 
    PacketPtr writebackBlk(CacheBlk *blk);
 
    PacketPtr writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id);
 
    virtual void memWriteback() override;
 
    virtual void memInvalidate() override;
 
    bool isDirty() const;
 
    bool inRange(Addr addr) const;
 
    Tick nextQueueReadyTime() const;
 
    const unsigned blkSize;
 
    const Cycles lookupLatency;
 
    const Cycles dataLatency;
 
    const Cycles forwardLatency;
 
    const Cycles fillLatency;
 
    const Cycles responseLatency;
 
    const bool sequentialAccess;
 
    const int numTarget;
 
    bool forwardSnoops;
 
    const enums::Clusivity clusivity;
 
    const bool isReadOnly;
 
    const bool replaceExpansions;
 
    const bool moveContractions;
 
    uint8_t blocked;
 
    uint64_t order;
 
    Cycles blockedCycle;
 
    MSHR *noTargetMSHR;
 
    Counter missCount;
 
    const AddrRangeList addrRanges;
 
  public:
    System *system;
 
    struct CacheCmdStats : public statistics::Group
    {
        CacheCmdStats(BaseCache &c, const std::string &name);
 
        void regStatsFromParent();
 
        const BaseCache &cache;
 
        statistics::Vector hits;
        statistics::Vector misses;
        statistics::Vector hitLatency;
        statistics::Vector missLatency;
        statistics::Formula accesses;
        statistics::Formula missRate;
        statistics::Formula avgMissLatency;
        statistics::Vector mshrHits;
        statistics::Vector mshrMisses;
        statistics::Vector mshrUncacheable;
        statistics::Vector mshrMissLatency;
        statistics::Vector mshrUncacheableLatency;
        statistics::Formula mshrMissRate;
        statistics::Formula avgMshrMissLatency;
        statistics::Formula avgMshrUncacheableLatency;
    };
 
    struct CacheStats : public statistics::Group
    {
        CacheStats(BaseCache &c);
 
        void regStats() override;
 
        CacheCmdStats &cmdStats(const PacketPtr p) {
            return *cmd[p->cmdToIndex()];
        }
 
        const BaseCache &cache;
 
        statistics::Formula demandHits;
        statistics::Formula overallHits;
        statistics::Formula demandHitLatency;
        statistics::Formula overallHitLatency;
 
        statistics::Formula demandMisses;
        statistics::Formula overallMisses;
 
        statistics::Formula demandMissLatency;
        statistics::Formula overallMissLatency;
 
        statistics::Formula demandAccesses;
        statistics::Formula overallAccesses;
 
        statistics::Formula demandMissRate;
        statistics::Formula overallMissRate;
 
        statistics::Formula demandAvgMissLatency;
        statistics::Formula overallAvgMissLatency;
 
        statistics::Vector blockedCycles;
        statistics::Vector blockedCauses;
 
        statistics::Formula avgBlocked;
 
        statistics::Vector writebacks;
 
        statistics::Formula demandMshrHits;
        statistics::Formula overallMshrHits;
 
        statistics::Formula demandMshrMisses;
        statistics::Formula overallMshrMisses;
 
        statistics::Formula overallMshrUncacheable;
 
        statistics::Formula demandMshrMissLatency;
        statistics::Formula overallMshrMissLatency;
 
        statistics::Formula overallMshrUncacheableLatency;
 
        statistics::Formula demandMshrMissRate;
        statistics::Formula overallMshrMissRate;
 
        statistics::Formula demandAvgMshrMissLatency;
        statistics::Formula overallAvgMshrMissLatency;
 
        statistics::Formula overallAvgMshrUncacheableLatency;
 
        statistics::Scalar replacements;
 
        statistics::Scalar dataExpansions;
 
        statistics::Scalar dataContractions;
 
        std::vector<std::unique_ptr<CacheCmdStats>> cmd;
    } stats;
 
    void regProbePoints() override;
 
  public:
    BaseCache(const BaseCacheParams &p, unsigned blk_size);
    ~BaseCache();
 
    void init() override;
 
    Port &getPort(const std::string &if_name,
                  PortID idx=InvalidPortID) override;
 
    unsigned
    getBlockSize() const
    {
        return blkSize;
    }
 
    const AddrRangeList &getAddrRanges() const { return addrRanges; }
 
    MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
    {
        MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
                                        pkt, time, order++,
                                        allocOnFill(pkt->cmd));
 
        if (mshrQueue.isFull()) {
            setBlocked((BlockedCause)MSHRQueue_MSHRs);
        }
 
        if (sched_send) {
            // schedule the send
            schedMemSideSendEvent(time);
        }
 
        return mshr;
    }
 
    void allocateWriteBuffer(PacketPtr pkt, Tick time)
    {
        // should only see writes or clean evicts here
        assert(pkt->isWrite() || pkt->cmd == MemCmd::CleanEvict);
 
        Addr blk_addr = pkt->getBlockAddr(blkSize);
 
        // If using compression, on evictions the block is decompressed and
        // the operation's latency is added to the payload delay. Consume
        // that payload delay here, meaning that the data is always stored
        // uncompressed in the writebuffer
        if (compressor) {
            time += pkt->payloadDelay;
            pkt->payloadDelay = 0;
        }
 
        WriteQueueEntry *wq_entry =
            writeBuffer.findMatch(blk_addr, pkt->isSecure());
        if (wq_entry && !wq_entry->inService) {
            DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
        }
 
        writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);
 
        if (writeBuffer.isFull()) {
            setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
        }
 
        // schedule the send
        schedMemSideSendEvent(time);
    }
 
    bool isBlocked() const
    {
        return blocked != 0;
    }
 
    void setBlocked(BlockedCause cause)
    {
        uint8_t flag = 1 << cause;
        if (blocked == 0) {
            stats.blockedCauses[cause]++;
            blockedCycle = curCycle();
            cpuSidePort.setBlocked();
        }
        blocked |= flag;
        DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
    }
 
    void clearBlocked(BlockedCause cause)
    {
        uint8_t flag = 1 << cause;
        blocked &= ~flag;
        DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
        if (blocked == 0) {
            stats.blockedCycles[cause] += curCycle() - blockedCycle;
            cpuSidePort.clearBlocked();
        }
    }
 
    void schedMemSideSendEvent(Tick time)
    {
        memSidePort.schedSendEvent(time);
    }
 
    bool inCache(Addr addr, bool is_secure) const {
        return tags->findBlock(addr, is_secure);
    }
 
    bool hasBeenPrefetched(Addr addr, bool is_secure) const {
        CacheBlk *block = tags->findBlock(addr, is_secure);
        return block && block->wasPrefetched();
    }
 
    bool hasBeenPrefetched(Addr addr, bool is_secure,
                           RequestorID requestor) const {
        CacheBlk *block = tags->findBlock(addr, is_secure);
        return block && block->wasPrefetched() &&
               (block->getSrcRequestorId() == requestor);
    }
 
    bool inMissQueue(Addr addr, bool is_secure) const {
        return mshrQueue.findMatch(addr, is_secure);
    }
 
    void incMissCount(PacketPtr pkt)
    {
        assert(pkt->req->requestorId() < system->maxRequestors());
        stats.cmdStats(pkt).misses[pkt->req->requestorId()]++;
        pkt->req->incAccessDepth();
        if (missCount) {
            --missCount;
            if (missCount == 0)
                exitSimLoop("A cache reached the maximum miss count");
        }
    }
    void incHitCount(PacketPtr pkt)
    {
        assert(pkt->req->requestorId() < system->maxRequestors());
        stats.cmdStats(pkt).hits[pkt->req->requestorId()]++;
    }
 
    bool coalesce() const;
 
 
    void writebackVisitor(CacheBlk &blk);
 
    void invalidateVisitor(CacheBlk &blk);
 
    virtual bool sendMSHRQueuePacket(MSHR* mshr);
 
    bool sendWriteQueuePacket(WriteQueueEntry* wq_entry);
 
    void serialize(CheckpointOut &cp) const override;
    void unserialize(CheckpointIn &cp) override;
};
 
class WriteAllocator : public SimObject
{
  public:
    WriteAllocator(const WriteAllocatorParams &p) :
        SimObject(p),
        coalesceLimit(p.coalesce_limit * p.block_size),
        noAllocateLimit(p.no_allocate_limit * p.block_size),
        delayThreshold(p.delay_threshold)
    {
        reset();
    }
 
    bool coalesce() const {
        return mode != WriteMode::ALLOCATE;
    }
 
    bool allocate() const {
        return mode != WriteMode::NO_ALLOCATE;
    }
 
    void reset() {
        mode = WriteMode::ALLOCATE;
        byteCount = 0;
        nextAddr = 0;
    }
 
    bool delay(Addr blk_addr) {
        if (delayCtr[blk_addr] > 0) {
            --delayCtr[blk_addr];
            return true;
        } else {
            return false;
        }
    }
 
    void resetDelay(Addr blk_addr) {
        delayCtr.erase(blk_addr);
    }
 
    void updateMode(Addr write_addr, unsigned write_size, Addr blk_addr);
 
  private:
    enum class WriteMode : char
    {
        ALLOCATE,
        COALESCE,
        NO_ALLOCATE,
    };
    WriteMode mode;
 
    Addr nextAddr;
 
    uint32_t byteCount;
 
    const uint32_t coalesceLimit;
    const uint32_t noAllocateLimit;
    const uint32_t delayThreshold;
 
    std::unordered_map<Addr, Counter> delayCtr;
};
 
} // namespace gem5
 
#endif //__MEM_CACHE_BASE_HH__