src/arch/amdgpu/vega/tlb_coalescer.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2021 Advanced Micro Devices, Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright notice,
  * this list of conditions and the following disclaimer.
  *
  * 2. 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.
  *
  * 3. Neither the name of the copyright holder 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 HOLDER 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 __ARCH_AMDGPU_VEGA_TLB_COALESCER_HH__
 #define __ARCH_AMDGPU_VEGA_TLB_COALESCER_HH__

 #include <list>
 #include <queue>
 #include <string>
 #include <vector>

 #include "arch/amdgpu/vega/tlb.hh"
 #include "base/statistics.hh"
 #include "mem/port.hh"
 #include "mem/request.hh"
 #include "params/VegaTLBCoalescer.hh"
 #include "sim/clocked_object.hh"

 namespace gem5
 {

 class Packet;
 class ThreadContext;

 /**
  * The VegaTLBCoalescer is a ClockedObject sitting on the front side (CPUSide)
  * of each TLB. It receives packets and issues coalesced requests to the
  * TLB below it. It controls how requests are coalesced (the rules)
  * and the permitted number of TLB probes per cycle (i.e., how many
  * coalesced requests it feeds the TLB per cycle).
  */
 class VegaTLBCoalescer : public ClockedObject
 {
   public:
     VegaTLBCoalescer(const VegaTLBCoalescerParams &p);
     ~VegaTLBCoalescer() { }

     // Number of TLB probes per cycle. Parameterizable - default 2.
     int TLBProbesPerCycle;

     // Consider coalescing across that many ticks.
     // Paraemterizable - default 1.
     int coalescingWindow;

     // Each coalesced request consists of multiple packets
     // that all fall within the same virtual page
     typedef std::vector<PacketPtr> coalescedReq;

     // disables coalescing when true
     bool disableCoalescing;

     /*
      * This is a hash map with <tick_index> as a key.
      * It contains a vector of coalescedReqs per <tick_index>.
      * Requests are buffered here until they can be issued to
      * the TLB, at which point they are copied to the
      * issuedTranslationsTable hash map.
      *
      * In terms of coalescing, we coalesce requests in a given
      * window of x cycles by using tick_index = issueTime/x as a
      * key, where x = coalescingWindow. issueTime is the issueTime
      * of the pkt from the ComputeUnit's perspective, but another
      * option is to change it to curTick(), so we coalesce based
      * on the receive time.
      */
     typedef std::map<Tick, std::vector<coalescedReq>> CoalescingFIFO;

     CoalescingFIFO coalescerFIFO;

     /*
      * issuedTranslationsTable: a hash_map indexed by virtual page
      * address. Each hash_map entry has a vector of PacketPtr associated
      * with it denoting the different packets that share an outstanding
      * coalesced translation request for the same virtual page.
      *
      * The rules that determine which requests we can coalesce are
      * specified in the canCoalesce() method.
      */
     typedef std::unordered_map<Addr, coalescedReq> CoalescingTable;

     CoalescingTable issuedTranslationsTable;

     // number of packets the coalescer receives
     statistics::Scalar uncoalescedAccesses;
     // number packets the coalescer send to the TLB
     statistics::Scalar coalescedAccesses;

     // Number of cycles the coalesced requests spend waiting in
     // coalescerFIFO. For each packet the coalescer receives we take into
     // account the number of all uncoalesced requests this pkt "represents"
     statistics::Scalar queuingCycles;

     // On average how much time a request from the
     // uncoalescedAccesses that reaches the TLB
     // spends waiting?
     statistics::Scalar localqueuingCycles;
     statistics::Scalar localCycles;
   // localqueuingCycles/uncoalescedAccesses
     statistics::Formula localLatency;
    // latency of a request to be completed
     statistics::Formula latency;

     bool canCoalesce(PacketPtr pkt1, PacketPtr pkt2);
     void updatePhysAddresses(PacketPtr pkt);
     void regStats() override;

     class CpuSidePort : public ResponsePort
     {
       public:
         CpuSidePort(const std::string &_name, VegaTLBCoalescer *tlb_coalescer,
                     PortID _index)
             : ResponsePort(_name, tlb_coalescer), coalescer(tlb_coalescer),
               index(_index) { }

       protected:
         VegaTLBCoalescer *coalescer;
         int index;

         virtual bool recvTimingReq(PacketPtr pkt);
         virtual Tick recvAtomic(PacketPtr pkt) { return 0; }
         virtual void recvFunctional(PacketPtr pkt);
         virtual void recvRangeChange() { }
         virtual void recvReqRetry();

         virtual void
         recvRespRetry()
         {
             fatal("recvRespRetry() is not implemented in the TLB "
                 "coalescer.\n");
         }

         virtual AddrRangeList getAddrRanges() const;
     };

     class MemSidePort : public RequestPort
     {
       public:
         MemSidePort(const std::string &_name, VegaTLBCoalescer *tlb_coalescer,
                     PortID _index)
             : RequestPort(_name, tlb_coalescer), coalescer(tlb_coalescer),
               index(_index) { }

         std::deque<PacketPtr> retries;

       protected:
         VegaTLBCoalescer *coalescer;
         int index;

         virtual bool recvTimingResp(PacketPtr pkt);
         virtual Tick recvAtomic(PacketPtr pkt) { return 0; }
         virtual void recvFunctional(PacketPtr pkt);
         virtual void recvRangeChange() { }
         virtual void recvReqRetry();

         virtual void
         recvRespRetry()
         {
             fatal("recvRespRetry() not implemented in TLB coalescer");
         }
     };

     // Coalescer response ports on the cpu Side
     std::vector<CpuSidePort*> cpuSidePort;
     // Coalescer request ports on the memory side
     std::vector<MemSidePort*> memSidePort;

     Port &getPort(const std::string &if_name,
                   PortID idx=InvalidPortID) override;

     void processProbeTLBEvent();
     /// This event issues the TLB probes
     EventFunctionWrapper probeTLBEvent;

     void processCleanupEvent();
     /// The cleanupEvent is scheduled after a TLBEvent triggers
     /// in order to free memory and do the required clean-up
     EventFunctionWrapper cleanupEvent;

     int tlb_level;
     int maxDownstream;
     unsigned int numDownstream;
     CpuSidePort *stalledPort;
     std::queue<CpuSidePort *> stalledPortsQueue;
     // enforce uniqueness in queue
     std::map<CpuSidePort *, CpuSidePort *> stalledPortsMap;

     unsigned int availDownstreamSlots() {
         assert(tlb_level == 1);
         return maxDownstream - numDownstream;
     }

     void insertStalledPortIfNotMapped(CpuSidePort *);
     bool mustStallCUPort(CpuSidePort *);

     bool stalledPorts() {
         assert(tlb_level == 1);
       return stalledPortsQueue.size() > 0;
     }

     void decrementNumDownstream() {
         assert(tlb_level == 1);
         assert(numDownstream > 0);
         numDownstream--;
     }

     void incrementNumDownstream() {
         assert(tlb_level == 1);
         assert(maxDownstream >= numDownstream);
         numDownstream++;
     }

     void unstallPorts();


     // this FIFO queue keeps track of the virt. page
     // addresses that are pending cleanup
     std::queue<Addr> cleanupQueue;
 };

 } // namespace gem5

 #endif // __ARCH_AMDGPU_VEGA_TLB_COALESCER_HH__
	/*
	* Copyright (c) 2021 Advanced Micro Devices, Inc.
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are met:
	*
	* 1. Redistributions of source code must retain the above copyright notice,
	* this list of conditions and the following disclaimer.
	*
	* 2. 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.
	*
	* 3. Neither the name of the copyright holder 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 HOLDER 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 __ARCH_AMDGPU_VEGA_TLB_COALESCER_HH__
	#define __ARCH_AMDGPU_VEGA_TLB_COALESCER_HH__

	#include <list>
	#include <queue>
	#include <string>
	#include <vector>

	#include "arch/amdgpu/vega/tlb.hh"
	#include "base/statistics.hh"
	#include "mem/port.hh"
	#include "mem/request.hh"
	#include "params/VegaTLBCoalescer.hh"
	#include "sim/clocked_object.hh"

	namespace gem5
	{

	class Packet;
	class ThreadContext;

	/**
	* The VegaTLBCoalescer is a ClockedObject sitting on the front side (CPUSide)
	* of each TLB. It receives packets and issues coalesced requests to the
	* TLB below it. It controls how requests are coalesced (the rules)
	* and the permitted number of TLB probes per cycle (i.e., how many
	* coalesced requests it feeds the TLB per cycle).
	*/
	class VegaTLBCoalescer : public ClockedObject
	{
	public:
	VegaTLBCoalescer(const VegaTLBCoalescerParams &p);
	~VegaTLBCoalescer() { }

	// Number of TLB probes per cycle. Parameterizable - default 2.
	int TLBProbesPerCycle;

	// Consider coalescing across that many ticks.
	// Paraemterizable - default 1.
	int coalescingWindow;

	// Each coalesced request consists of multiple packets
	// that all fall within the same virtual page
	typedef std::vector<PacketPtr> coalescedReq;

	// disables coalescing when true
	bool disableCoalescing;

	/*
	* This is a hash map with <tick_index> as a key.
	* It contains a vector of coalescedReqs per <tick_index>.
	* Requests are buffered here until they can be issued to
	* the TLB, at which point they are copied to the
	* issuedTranslationsTable hash map.
	*
	* In terms of coalescing, we coalesce requests in a given
	* window of x cycles by using tick_index = issueTime/x as a
	* key, where x = coalescingWindow. issueTime is the issueTime
	* of the pkt from the ComputeUnit's perspective, but another
	* option is to change it to curTick(), so we coalesce based
	* on the receive time.
	*/
	typedef std::map<Tick, std::vector<coalescedReq>> CoalescingFIFO;

	CoalescingFIFO coalescerFIFO;

	/*
	* issuedTranslationsTable: a hash_map indexed by virtual page
	* address. Each hash_map entry has a vector of PacketPtr associated
	* with it denoting the different packets that share an outstanding
	* coalesced translation request for the same virtual page.
	*
	* The rules that determine which requests we can coalesce are
	* specified in the canCoalesce() method.
	*/
	typedef std::unordered_map<Addr, coalescedReq> CoalescingTable;

	CoalescingTable issuedTranslationsTable;

	// number of packets the coalescer receives
	statistics::Scalar uncoalescedAccesses;
	// number packets the coalescer send to the TLB
	statistics::Scalar coalescedAccesses;

	// Number of cycles the coalesced requests spend waiting in
	// coalescerFIFO. For each packet the coalescer receives we take into
	// account the number of all uncoalesced requests this pkt "represents"
	statistics::Scalar queuingCycles;

	// On average how much time a request from the
	// uncoalescedAccesses that reaches the TLB
	// spends waiting?
	statistics::Scalar localqueuingCycles;
	statistics::Scalar localCycles;
	// localqueuingCycles/uncoalescedAccesses
	statistics::Formula localLatency;
	// latency of a request to be completed
	statistics::Formula latency;

	bool canCoalesce(PacketPtr pkt1, PacketPtr pkt2);
	void updatePhysAddresses(PacketPtr pkt);
	void regStats() override;

	class CpuSidePort : public ResponsePort
	{
	public:
	CpuSidePort(const std::string &_name, VegaTLBCoalescer *tlb_coalescer,
	PortID _index)
	: ResponsePort(_name, tlb_coalescer), coalescer(tlb_coalescer),
	index(_index) { }

	protected:
	VegaTLBCoalescer *coalescer;
	int index;

	virtual bool recvTimingReq(PacketPtr pkt);
	virtual Tick recvAtomic(PacketPtr pkt) { return 0; }
	virtual void recvFunctional(PacketPtr pkt);
	virtual void recvRangeChange() { }
	virtual void recvReqRetry();

	virtual void
	recvRespRetry()
	{
	fatal("recvRespRetry() is not implemented in the TLB "
	"coalescer.\n");
	}

	virtual AddrRangeList getAddrRanges() const;
	};

	class MemSidePort : public RequestPort
	{
	public:
	MemSidePort(const std::string &_name, VegaTLBCoalescer *tlb_coalescer,
	PortID _index)
	: RequestPort(_name, tlb_coalescer), coalescer(tlb_coalescer),
	index(_index) { }

	std::deque<PacketPtr> retries;

	protected:
	VegaTLBCoalescer *coalescer;
	int index;

	virtual bool recvTimingResp(PacketPtr pkt);
	virtual Tick recvAtomic(PacketPtr pkt) { return 0; }
	virtual void recvFunctional(PacketPtr pkt);
	virtual void recvRangeChange() { }
	virtual void recvReqRetry();

	virtual void
	recvRespRetry()
	{
	fatal("recvRespRetry() not implemented in TLB coalescer");
	}
	};

	// Coalescer response ports on the cpu Side
	std::vector<CpuSidePort*> cpuSidePort;
	// Coalescer request ports on the memory side
	std::vector<MemSidePort*> memSidePort;

	Port &getPort(const std::string &if_name,
	PortID idx=InvalidPortID) override;

	void processProbeTLBEvent();
	/// This event issues the TLB probes
	EventFunctionWrapper probeTLBEvent;

	void processCleanupEvent();
	/// The cleanupEvent is scheduled after a TLBEvent triggers
	/// in order to free memory and do the required clean-up
	EventFunctionWrapper cleanupEvent;

	int tlb_level;
	int maxDownstream;
	unsigned int numDownstream;
	CpuSidePort *stalledPort;
	std::queue<CpuSidePort *> stalledPortsQueue;
	// enforce uniqueness in queue
	std::map<CpuSidePort , CpuSidePort > stalledPortsMap;

	unsigned int availDownstreamSlots() {
	assert(tlb_level == 1);
	return maxDownstream - numDownstream;
	}

	void insertStalledPortIfNotMapped(CpuSidePort *);
	bool mustStallCUPort(CpuSidePort *);

	bool stalledPorts() {
	assert(tlb_level == 1);
	return stalledPortsQueue.size() > 0;
	}

	void decrementNumDownstream() {
	assert(tlb_level == 1);
	assert(numDownstream > 0);
	numDownstream--;
	}

	void incrementNumDownstream() {
	assert(tlb_level == 1);
	assert(maxDownstream >= numDownstream);
	numDownstream++;
	}

	void unstallPorts();


	// this FIFO queue keeps track of the virt. page
	// addresses that are pending cleanup
	std::queue<Addr> cleanupQueue;
	};

	} // namespace gem5

	#endif // __ARCH_AMDGPU_VEGA_TLB_COALESCER_HH__