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Diffstat (limited to 'src/mem/cache/coherence/coherence_protocol.hh')
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diff --git a/src/mem/cache/coherence/coherence_protocol.hh b/src/mem/cache/coherence/coherence_protocol.hh new file mode 100644 index 000000000..21351ace4 --- /dev/null +++ b/src/mem/cache/coherence/coherence_protocol.hh @@ -0,0 +1,263 @@ +/* + * Copyright (c) 2002-2005 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 + * 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: Erik Hallnor + * Ron Dreslinski + * Steve Reinhardt + */ + +/** + * @file + * Declaration of CoherenceProcotol a basic coherence policy. + */ +#ifndef __COHERENCE_PROTOCOL_HH__ +#define __COHERENCE_PROTOCOL_HH__ + +#include <string> + +#include "sim/sim_object.hh" +#include "mem/packet.hh" +#include "mem/cache/cache_blk.hh" +#include "base/statistics.hh" + +class BaseCache; +class MSHR; + +/** + * A simple coherence policy for the memory hierarchy. Currently implements + * MSI, MESI, and MOESI protocols. + */ +class CoherenceProtocol : public SimObject +{ + public: + /** + * Contruct and initialize this policy. + * @param name The name of this policy. + * @param protocol The string representation of the protocol to use. + * @param doUpgrades True if bus upgrades should be used. + */ + CoherenceProtocol(const std::string &name, const std::string &protocol, + const bool doUpgrades); + + /** + * Destructor. + */ + virtual ~CoherenceProtocol() {}; + + /** + * Register statistics + */ + virtual void regStats(); + + /** + * Get the proper bus command for the given command and status. + * @param cmd The request's command. + * @param status The current state of the cache block. + * @param mshr The MSHR matching the request. + * @return The proper bus command, as determined by the protocol. + */ + Packet::Command getBusCmd(Packet::Command cmd, CacheBlk::State status, + MSHR *mshr = NULL); + + /** + * Return the proper state given the current state and the bus response. + * @param req The bus response. + * @param oldState The current block state. + * @return The new state. + */ + CacheBlk::State getNewState(Packet * &pkt, + CacheBlk::State oldState); + + /** + * Handle snooped bus requests. + * @param cache The cache that snooped the request. + * @param req The snooped bus request. + * @param blk The cache block corresponding to the request, if any. + * @param mshr The MSHR corresponding to the request, if any. + * @param new_state The new coherence state of the block. + * @return True if the request should be satisfied locally. + */ + bool handleBusRequest(BaseCache *cache, Packet * &pkt, CacheBlk *blk, + MSHR *mshr, CacheBlk::State &new_state); + + protected: + /** Snoop function type. */ + typedef bool (*SnoopFuncType)(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + // + // Standard snoop transition functions + // + + /** + * Do nothing transition. + */ + static bool nullTransition(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Invalid transition, basically panic. + */ + static bool invalidTransition(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Invalidate block, move to Invalid state. + */ + static bool invalidateTrans(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Supply data, no state transition. + */ + static bool supplyTrans(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Supply data and go to Shared state. + */ + static bool supplyAndGotoSharedTrans(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Supply data and go to Owned state. + */ + static bool supplyAndGotoOwnedTrans(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Invalidate block, supply data, and go to Invalid state. + */ + static bool supplyAndInvalidateTrans(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Assert the shared line for a block that is shared/exclusive. + */ + static bool assertShared(BaseCache *, Packet *&, CacheBlk *, + MSHR *, CacheBlk::State&); + + /** + * Definition of protocol state transitions. + */ + class StateTransition + { + friend class CoherenceProtocol; + + /** The bus command of this transition. */ + Packet::Command busCmd; + /** The state to transition to. */ + int newState; + /** The snoop function for this transition. */ + SnoopFuncType snoopFunc; + + /** + * Constructor, defaults to invalid transition. + */ + StateTransition(); + + /** + * Initialize bus command. + * @param cmd The bus command to use. + */ + void onRequest(Packet::Command cmd) + { + busCmd = cmd; + } + + /** + * Set the transition state. + * @param s The new state. + */ + void onResponse(CacheBlk::State s) + { + newState = s; + } + + /** + * Initialize the snoop function. + * @param f The new snoop function. + */ + void onSnoop(SnoopFuncType f) + { + snoopFunc = f; + } + }; + + friend class CoherenceProtocol::StateTransition; + + /** Mask to select status bits relevant to coherence protocol. */ + const static CacheBlk::State + stateMask = BlkValid | BlkWritable | BlkDirty; + + /** The Modified (M) state. */ + const static CacheBlk::State + Modified = BlkValid | BlkWritable | BlkDirty; + /** The Owned (O) state. */ + const static CacheBlk::State + Owned = BlkValid | BlkDirty; + /** The Exclusive (E) state. */ + const static CacheBlk::State + Exclusive = BlkValid | BlkWritable; + /** The Shared (S) state. */ + const static CacheBlk::State + Shared = BlkValid; + /** The Invalid (I) state. */ + const static CacheBlk::State + Invalid = 0; + + /** + * Maximum state encoding value (used to size transition lookup + * table). Could be more than number of states, depends on + * encoding of status bits. + */ + const static int stateMax = stateMask; + + /** + * The table of all possible transitions, organized by starting state and + * request command. + */ + StateTransition transitionTable[stateMax+1][NUM_MEM_CMDS]; + + /** + * @addtogroup CoherenceStatistics + * @{ + */ + /** + * State accesses from parent cache. + */ + Stats::Scalar<> requestCount[stateMax+1][NUM_MEM_CMDS]; + /** + * State accesses from snooped requests. + */ + Stats::Scalar<> snoopCount[stateMax+1][NUM_MEM_CMDS]; + /** + * @} + */ +}; + +#endif // __COHERENCE_PROTOCOL_HH__ |