src/mem/cache/prefetch/stride.cc - public/gem5 - Git at Google

 /*
  * Copyright (c) 2018 Inria
  * Copyright (c) 2012-2013, 2015 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) 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.
  */

 /**
  * @file
  * Stride Prefetcher template instantiations.
  */

 #include "mem/cache/prefetch/stride.hh"

 #include <cassert>

 #include "base/intmath.hh"
 #include "base/logging.hh"
 #include "base/random.hh"
 #include "base/trace.hh"
 #include "debug/HWPrefetch.hh"
 #include "mem/cache/prefetch/associative_set_impl.hh"
 #include "mem/cache/replacement_policies/base.hh"
 #include "params/StridePrefetcher.hh"

 namespace Prefetcher {

 Stride::StrideEntry::StrideEntry(const SatCounter8& init_confidence)
   : TaggedEntry(), confidence(init_confidence)
 {
     invalidate();
 }

 void
 Stride::StrideEntry::invalidate()
 {
     TaggedEntry::invalidate();
     lastAddr = 0;
     stride = 0;
     confidence.reset();
 }

 Stride::Stride(const StridePrefetcherParams &p)
   : Queued(p),
     initConfidence(p.confidence_counter_bits, p.initial_confidence),
     threshConf(p.confidence_threshold/100.0),
     useRequestorId(p.use_requestor_id),
     degree(p.degree),
     pcTableInfo(p.table_assoc, p.table_entries, p.table_indexing_policy,
         p.table_replacement_policy)
 {
 }

 Stride::PCTable*
 Stride::findTable(int context)
 {
     // Check if table for given context exists
     auto it = pcTables.find(context);
     if (it != pcTables.end())
         return &it->second;

     // If table does not exist yet, create one
     return allocateNewContext(context);
 }

 Stride::PCTable*
 Stride::allocateNewContext(int context)
 {
     // Create new table
     auto insertion_result = pcTables.insert(std::make_pair(context,
         PCTable(pcTableInfo.assoc, pcTableInfo.numEntries,
         pcTableInfo.indexingPolicy, pcTableInfo.replacementPolicy,
         StrideEntry(initConfidence))));

     DPRINTF(HWPrefetch, "Adding context %i with stride entries\n", context);

     // Get iterator to new pc table, and then return a pointer to the new table
     return &(insertion_result.first->second);
 }

 void
 Stride::calculatePrefetch(const PrefetchInfo &pfi,
                                     std::vector<AddrPriority> &addresses)
 {
     if (!pfi.hasPC()) {
         DPRINTF(HWPrefetch, "Ignoring request with no PC.\n");
         return;
     }

     // Get required packet info
     Addr pf_addr = pfi.getAddr();
     Addr pc = pfi.getPC();
     bool is_secure = pfi.isSecure();
     RequestorID requestor_id = useRequestorId ? pfi.getRequestorId() : 0;

     // Get corresponding pc table
     PCTable* pcTable = findTable(requestor_id);

     // Search for entry in the pc table
     StrideEntry *entry = pcTable->findEntry(pc, is_secure);

     if (entry != nullptr) {
         pcTable->accessEntry(entry);

         // Hit in table
         int new_stride = pf_addr - entry->lastAddr;
         bool stride_match = (new_stride == entry->stride);

         // Adjust confidence for stride entry
         if (stride_match && new_stride != 0) {
             entry->confidence++;
         } else {
             entry->confidence--;
             // If confidence has dropped below the threshold, train new stride
             if (entry->confidence.calcSaturation() < threshConf) {
                 entry->stride = new_stride;
             }
         }

         DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), "
                 "conf %d\n", pc, pf_addr, is_secure ? "s" : "ns",
                 new_stride, stride_match ? "match" : "change",
                 (int)entry->confidence);

         entry->lastAddr = pf_addr;

         // Abort prefetch generation if below confidence threshold
         if (entry->confidence.calcSaturation() < threshConf) {
             return;
         }

         // Generate up to degree prefetches
         for (int d = 1; d <= degree; d++) {
             // Round strides up to atleast 1 cacheline
             int prefetch_stride = new_stride;
             if (abs(new_stride) < blkSize) {
                 prefetch_stride = (new_stride < 0) ? -blkSize : blkSize;
             }

             Addr new_addr = pf_addr + d * prefetch_stride;
             addresses.push_back(AddrPriority(new_addr, 0));
         }
     } else {
         // Miss in table
         DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pf_addr,
                 is_secure ? "s" : "ns");

         StrideEntry* entry = pcTable->findVictim(pc);

         // Insert new entry's data
         entry->lastAddr = pf_addr;
         pcTable->insertEntry(pc, is_secure, entry);
     }
 }

 uint32_t
 StridePrefetcherHashedSetAssociative::extractSet(const Addr pc) const
 {
     const Addr hash1 = pc >> 1;
     const Addr hash2 = hash1 >> tagShift;
     return (hash1 ^ hash2) & setMask;
 }

 Addr
 StridePrefetcherHashedSetAssociative::extractTag(const Addr addr) const
 {
     return addr;
 }

 } // namespace Prefetcher
	/*
	* Copyright (c) 2018 Inria
	* Copyright (c) 2012-2013, 2015 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) 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.
	*/

	/**
	* @file
	* Stride Prefetcher template instantiations.
	*/

	#include "mem/cache/prefetch/stride.hh"

	#include <cassert>

	#include "base/intmath.hh"
	#include "base/logging.hh"
	#include "base/random.hh"
	#include "base/trace.hh"
	#include "debug/HWPrefetch.hh"
	#include "mem/cache/prefetch/associative_set_impl.hh"
	#include "mem/cache/replacement_policies/base.hh"
	#include "params/StridePrefetcher.hh"

	namespace Prefetcher {

	Stride::StrideEntry::StrideEntry(const SatCounter8& init_confidence)
	: TaggedEntry(), confidence(init_confidence)
	{
	invalidate();
	}

	void
	Stride::StrideEntry::invalidate()
	{
	TaggedEntry::invalidate();
	lastAddr = 0;
	stride = 0;
	confidence.reset();
	}

	Stride::Stride(const StridePrefetcherParams &p)
	: Queued(p),
	initConfidence(p.confidence_counter_bits, p.initial_confidence),
	threshConf(p.confidence_threshold/100.0),
	useRequestorId(p.use_requestor_id),
	degree(p.degree),
	pcTableInfo(p.table_assoc, p.table_entries, p.table_indexing_policy,
	p.table_replacement_policy)
	{
	}

	Stride::PCTable*
	Stride::findTable(int context)
	{
	// Check if table for given context exists
	auto it = pcTables.find(context);
	if (it != pcTables.end())
	return &it->second;

	// If table does not exist yet, create one
	return allocateNewContext(context);
	}

	Stride::PCTable*
	Stride::allocateNewContext(int context)
	{
	// Create new table
	auto insertion_result = pcTables.insert(std::make_pair(context,
	PCTable(pcTableInfo.assoc, pcTableInfo.numEntries,
	pcTableInfo.indexingPolicy, pcTableInfo.replacementPolicy,
	StrideEntry(initConfidence))));

	DPRINTF(HWPrefetch, "Adding context %i with stride entries\n", context);

	// Get iterator to new pc table, and then return a pointer to the new table
	return &(insertion_result.first->second);
	}

	void
	Stride::calculatePrefetch(const PrefetchInfo &pfi,
	std::vector<AddrPriority> &addresses)
	{
	if (!pfi.hasPC()) {
	DPRINTF(HWPrefetch, "Ignoring request with no PC.\n");
	return;
	}

	// Get required packet info
	Addr pf_addr = pfi.getAddr();
	Addr pc = pfi.getPC();
	bool is_secure = pfi.isSecure();
	RequestorID requestor_id = useRequestorId ? pfi.getRequestorId() : 0;

	// Get corresponding pc table
	PCTable* pcTable = findTable(requestor_id);

	// Search for entry in the pc table
	StrideEntry *entry = pcTable->findEntry(pc, is_secure);

	if (entry != nullptr) {
	pcTable->accessEntry(entry);

	// Hit in table
	int new_stride = pf_addr - entry->lastAddr;
	bool stride_match = (new_stride == entry->stride);

	// Adjust confidence for stride entry
	if (stride_match && new_stride != 0) {
	entry->confidence++;
	} else {
	entry->confidence--;
	// If confidence has dropped below the threshold, train new stride
	if (entry->confidence.calcSaturation() < threshConf) {
	entry->stride = new_stride;
	}
	}

	DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), "
	"conf %d\n", pc, pf_addr, is_secure ? "s" : "ns",
	new_stride, stride_match ? "match" : "change",
	(int)entry->confidence);

	entry->lastAddr = pf_addr;

	// Abort prefetch generation if below confidence threshold
	if (entry->confidence.calcSaturation() < threshConf) {
	return;
	}

	// Generate up to degree prefetches
	for (int d = 1; d <= degree; d++) {
	// Round strides up to atleast 1 cacheline
	int prefetch_stride = new_stride;
	if (abs(new_stride) < blkSize) {
	prefetch_stride = (new_stride < 0) ? -blkSize : blkSize;
	}

	Addr new_addr = pf_addr + d * prefetch_stride;
	addresses.push_back(AddrPriority(new_addr, 0));
	}
	} else {
	// Miss in table
	DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pf_addr,
	is_secure ? "s" : "ns");

	StrideEntry* entry = pcTable->findVictim(pc);

	// Insert new entry's data
	entry->lastAddr = pf_addr;
	pcTable->insertEntry(pc, is_secure, entry);
	}
	}

	uint32_t
	StridePrefetcherHashedSetAssociative::extractSet(const Addr pc) const
	{
	const Addr hash1 = pc >> 1;
	const Addr hash2 = hash1 >> tagShift;
	return (hash1 ^ hash2) & setMask;
	}

	Addr
	StridePrefetcherHashedSetAssociative::extractTag(const Addr addr) const
	{
	return addr;
	}

	} // namespace Prefetcher