1/* 2 * Copyright (c) 2012-2013, 2015 ARM Limited 3 * All rights reserved 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software 9 * licensed hereunder. You may use the software subject to the license 10 * terms below provided that you ensure that this notice is replicated 11 * unmodified and in its entirety in all distributions of the software, 12 * modified or unmodified, in source code or in binary form. 13 * 14 * Copyright (c) 2005 The Regents of The University of Michigan 15 * All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions are 19 * met: redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer; 21 * redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution; 24 * neither the name of the copyright holders nor the names of its 25 * contributors may be used to endorse or promote products derived from 26 * this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 39 * 40 * Authors: Ron Dreslinski 41 * Steve Reinhardt 42 */ 43 44/** 45 * @file 46 * Stride Prefetcher template instantiations. 47 */ 48 49#include "mem/cache/prefetch/stride.hh" 50 51#include <cassert> 52 53#include "base/intmath.hh" 54#include "base/logging.hh" 55#include "base/random.hh" 56#include "base/trace.hh" 57#include "debug/HWPrefetch.hh" 58#include "params/StridePrefetcher.hh" 59 60StridePrefetcher::StridePrefetcher(const StridePrefetcherParams *p) 61 : QueuedPrefetcher(p), 62 maxConf(p->max_conf), 63 threshConf(p->thresh_conf), 64 minConf(p->min_conf), 65 startConf(p->start_conf), 66 pcTableAssoc(p->table_assoc), 67 pcTableSets(p->table_sets), 68 useMasterId(p->use_master_id),
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69 degree(p->degree),
70 pcTable(pcTableAssoc, pcTableSets, name())
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69 degree(p->degree) |
70{ 71 assert(isPowerOf2(pcTableSets)); 72} 73
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75std::vector<std::vector<StridePrefetcher::StrideEntry>>&
76StridePrefetcher::PCTable::allocateNewContext(int context)
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74StridePrefetcher::PCTable* 75StridePrefetcher::findTable(int context) |
76{
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78 auto res = entries.insert(std::make_pair(context,
79 std::vector<std::vector<StrideEntry>>(pcTableSets)));
80 auto it = res.first;
81 chatty_assert(res.second, "Allocating an already created context\n");
82 assert(it->first == context);
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77 // Check if table for given context exists 78 auto it = pcTables.find(context); 79 if (it != pcTables.end()) 80 return &it->second; |
81
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82 // If table does not exist yet, create one 83 return allocateNewContext(context); 84} 85 86StridePrefetcher::PCTable* 87StridePrefetcher::allocateNewContext(int context) 88{ 89 // Create new table 90 auto insertion_result = pcTables.insert(std::make_pair(context, 91 PCTable(pcTableAssoc, pcTableSets, name()))); 92 |
93 DPRINTF(HWPrefetch, "Adding context %i with stride entries\n", context); 94
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86 std::vector<std::vector<StrideEntry>>& table = it->second;
87 for (auto& set : table) {
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95 // Get iterator to new pc table, and then return a pointer to the new table 96 return &(insertion_result.first->second); 97} 98 99StridePrefetcher::PCTable::PCTable(int assoc, int sets, const std::string name) 100 : pcTableAssoc(assoc), pcTableSets(sets), _name(name), entries(pcTableSets) 101{ 102 for (auto& set : entries) { |
103 set.resize(pcTableAssoc); 104 }
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90 return table;
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105} 106 107StridePrefetcher::PCTable::~PCTable() 108{ 109} 110 111void 112StridePrefetcher::calculatePrefetch(const PacketPtr &pkt, 113 std::vector<AddrPriority> &addresses) 114{ 115 if (!pkt->req->hasPC()) { 116 DPRINTF(HWPrefetch, "Ignoring request with no PC.\n"); 117 return; 118 } 119 120 // Get required packet info 121 Addr pkt_addr = pkt->getAddr(); 122 Addr pc = pkt->req->getPC(); 123 bool is_secure = pkt->isSecure(); 124 MasterID master_id = useMasterId ? pkt->req->masterId() : 0; 125
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126 // Get corresponding pc table 127 PCTable* pcTable = findTable(master_id); 128 |
129 // Search for entry in the pc table
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113 StrideEntry *entry = findEntry(pc, is_secure, master_id);
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130 StrideEntry *entry = pcTable->findEntry(pc, is_secure); |
131 132 if (entry != nullptr) { 133 // Hit in table 134 int new_stride = pkt_addr - entry->lastAddr; 135 bool stride_match = (new_stride == entry->stride); 136 137 // Adjust confidence for stride entry 138 if (stride_match && new_stride != 0) { 139 if (entry->confidence < maxConf) 140 entry->confidence++; 141 } else { 142 if (entry->confidence > minConf) 143 entry->confidence--; 144 // If confidence has dropped below the threshold, train new stride 145 if (entry->confidence < threshConf) 146 entry->stride = new_stride; 147 } 148 149 DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), " 150 "conf %d\n", pc, pkt_addr, is_secure ? "s" : "ns", new_stride, 151 stride_match ? "match" : "change", 152 entry->confidence); 153 154 entry->lastAddr = pkt_addr; 155 156 // Abort prefetch generation if below confidence threshold 157 if (entry->confidence < threshConf) 158 return; 159 160 // Generate up to degree prefetches 161 for (int d = 1; d <= degree; d++) { 162 // Round strides up to atleast 1 cacheline 163 int prefetch_stride = new_stride; 164 if (abs(new_stride) < blkSize) { 165 prefetch_stride = (new_stride < 0) ? -blkSize : blkSize; 166 } 167 168 Addr new_addr = pkt_addr + d * prefetch_stride; 169 if (samePage(pkt_addr, new_addr)) { 170 DPRINTF(HWPrefetch, "Queuing prefetch to %#x.\n", new_addr); 171 addresses.push_back(AddrPriority(new_addr, 0)); 172 } else { 173 // Record the number of page crossing prefetches generated 174 pfSpanPage += degree - d + 1; 175 DPRINTF(HWPrefetch, "Ignoring page crossing prefetch.\n"); 176 return; 177 } 178 } 179 } else { 180 // Miss in table 181 DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pkt_addr, 182 is_secure ? "s" : "ns"); 183
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167 StrideEntry* entry = pcTableVictim(pc, master_id);
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184 StrideEntry* entry = pcTable->findVictim(pc); |
185 entry->instAddr = pc; 186 entry->lastAddr = pkt_addr; 187 entry->isSecure= is_secure; 188 entry->stride = 0; 189 entry->confidence = startConf; 190 } 191} 192 193inline Addr
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177StridePrefetcher::pcHash(Addr pc) const
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194StridePrefetcher::PCTable::pcHash(Addr pc) const |
195{ 196 Addr hash1 = pc >> 1; 197 Addr hash2 = hash1 >> floorLog2(pcTableSets); 198 return (hash1 ^ hash2) & (Addr)(pcTableSets - 1); 199} 200 201inline StridePrefetcher::StrideEntry*
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185StridePrefetcher::pcTableVictim(Addr pc, int master_id)
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202StridePrefetcher::PCTable::findVictim(Addr pc) |
203{ 204 // Rand replacement for now 205 int set = pcHash(pc); 206 int way = random_mt.random<int>(0, pcTableAssoc - 1); 207 208 DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n", set, way);
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192 return &pcTable[master_id][set][way];
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209 return &entries[set][way]; |
210} 211 212inline StridePrefetcher::StrideEntry*
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196StridePrefetcher::findEntry(Addr pc, bool is_secure, int master_id)
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213StridePrefetcher::PCTable::findEntry(Addr pc, bool is_secure) |
214{ 215 int set = pcHash(pc);
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199 std::vector<StrideEntry>& set_entries = pcTable[master_id][set];
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216 std::vector<StrideEntry>& set_entries = entries[set]; |
217 for (int way = 0; way < pcTableAssoc; way++) { 218 StrideEntry* entry = &set_entries[way]; 219 // Search ways for match 220 if ((entry->instAddr == pc) && (entry->isSecure == is_secure)) { 221 DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way); 222 return entry; 223 } 224 } 225 return nullptr; 226} 227 228StridePrefetcher* 229StridePrefetcherParams::create() 230{ 231 return new StridePrefetcher(this); 232}
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