1/* 2 * Copyright (c) 2012-2013 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 --- 32 unchanged lines hidden (view full) --- 41 * Steve Reinhardt 42 */ 43 44/** 45 * @file 46 * Stride Prefetcher template instantiations. 47 */ 48 |
49#include "debug/HWPrefetch.hh" 50#include "mem/cache/prefetch/stride.hh" 51 |
52StridePrefetcher::StridePrefetcher(const StridePrefetcherParams *p) 53 : QueuedPrefetcher(p), 54 maxConf(p->max_conf), 55 threshConf(p->thresh_conf), 56 minConf(p->min_conf), 57 startConf(p->start_conf), 58 pcTableAssoc(p->table_assoc), 59 pcTableSets(p->table_sets), 60 useMasterId(p->use_master_id), 61 degree(p->degree) 62{ 63 // Don't consult stride prefetcher on instruction accesses 64 onInst = false; 65 66 assert(isPowerOf2(pcTableSets)); 67 68 for (int c = 0; c < maxContexts; c++) { 69 pcTable[c] = new StrideEntry*[pcTableSets]; 70 for (int s = 0; s < pcTableSets; s++) { 71 pcTable[c][s] = new StrideEntry[pcTableAssoc]; 72 } 73 } 74} 75 76StridePrefetcher::~StridePrefetcher() 77{ 78 for (int c = 0; c < maxContexts; c++) { 79 for (int s = 0; s < pcTableSets; s++) { 80 delete[] pcTable[c][s]; 81 } 82 } 83} 84 |
85void |
86StridePrefetcher::calculatePrefetch(const PacketPtr &pkt, 87 std::vector<Addr> &addresses) |
88{ 89 if (!pkt->req->hasPC()) { |
90 DPRINTF(HWPrefetch, "Ignoring request with no PC.\n"); |
91 return; 92 } 93 |
94 // Get required packet info 95 Addr pkt_addr = pkt->getAddr(); 96 Addr pc = pkt->req->getPC(); |
97 bool is_secure = pkt->isSecure(); 98 MasterID master_id = useMasterId ? pkt->req->masterId() : 0; |
99 |
100 assert(master_id < maxContexts); |
101 |
102 // Lookup pc-based information 103 StrideEntry *entry; |
104 |
105 if(pcTableHit(pc, is_secure, master_id, entry)) { |
106 // Hit in table |
107 int new_stride = pkt_addr - entry->lastAddr; 108 bool stride_match = (new_stride == entry->stride); |
109 |
110 // Adjust confidence for stride entry |
111 if (stride_match && new_stride != 0) { |
112 if (entry->confidence < maxConf) 113 entry->confidence++; |
114 } else { |
115 if (entry->confidence > minConf) 116 entry->confidence--; 117 // If confidence has dropped below the threshold, train new stride 118 if (entry->confidence < threshConf) 119 entry->stride = new_stride; |
120 } 121 |
122 DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), " 123 "conf %d\n", pc, pkt_addr, is_secure ? "s" : "ns", new_stride, |
124 stride_match ? "match" : "change", |
125 entry->confidence); |
126 |
127 entry->lastAddr = pkt_addr; |
128 |
129 // Abort prefetch generation if below confidence threshold 130 if (entry->confidence < threshConf) |
131 return; 132 |
133 // Generate up to degree prefetches |
134 for (int d = 1; d <= degree; d++) { |
135 // Round strides up to atleast 1 cacheline 136 int prefetch_stride = new_stride; 137 if (abs(new_stride) < blkSize) { 138 prefetch_stride = (new_stride < 0) ? -blkSize : blkSize; 139 } 140 141 Addr new_addr = pkt_addr + d * prefetch_stride; 142 if (samePage(pkt_addr, new_addr)) { 143 DPRINTF(HWPrefetch, "Queuing prefetch to %#x.\n", new_addr); 144 addresses.push_back(new_addr); 145 } else { 146 // Record the number of page crossing prefetches generated |
147 pfSpanPage += degree - d + 1; |
148 DPRINTF(HWPrefetch, "Ignoring page crossing prefetch.\n"); |
149 return; |
150 } 151 } 152 } else { 153 // Miss in table |
154 DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pkt_addr, |
155 is_secure ? "s" : "ns"); 156 |
157 StrideEntry* entry = pcTableVictim(pc, master_id); 158 entry->instAddr = pc; 159 entry->lastAddr = pkt_addr; 160 entry->isSecure= is_secure; 161 entry->stride = 0; 162 entry->confidence = startConf; 163 } 164} |
165 |
166inline Addr 167StridePrefetcher::pcHash(Addr pc) const 168{ 169 Addr hash1 = pc >> 1; 170 Addr hash2 = hash1 >> floorLog2(pcTableSets); 171 return (hash1 ^ hash2) & (Addr)(pcTableSets - 1); 172} |
173 |
174inline StridePrefetcher::StrideEntry* 175StridePrefetcher::pcTableVictim(Addr pc, int master_id) 176{ 177 // Rand replacement for now 178 int set = pcHash(pc); 179 int way = rand() % pcTableAssoc; 180 181 DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n", set, way); 182 return &pcTable[master_id][set][way]; 183} 184 185inline bool 186StridePrefetcher::pcTableHit(Addr pc, bool is_secure, int master_id, 187 StrideEntry* &entry) 188{ 189 int set = pcHash(pc); 190 StrideEntry* set_entries = pcTable[master_id][set]; 191 for (int way = 0; way < pcTableAssoc; way++) { 192 // Search ways for match 193 if (set_entries[way].instAddr == pc && 194 set_entries[way].isSecure == is_secure) { 195 DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way); 196 entry = &set_entries[way]; 197 return true; 198 } |
199 } |
200 return false; |
201} 202 |
203StridePrefetcher* 204StridePrefetcherParams::create() 205{ |
206 return new StridePrefetcher(this); |
207} |