stride.cc revision 10627:63edd4a1243f
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 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 "base/random.hh" 50#include "debug/HWPrefetch.hh" 51#include "mem/cache/prefetch/stride.hh" 52 53StridePrefetcher::StridePrefetcher(const StridePrefetcherParams *p) 54 : QueuedPrefetcher(p), 55 maxConf(p->max_conf), 56 threshConf(p->thresh_conf), 57 minConf(p->min_conf), 58 startConf(p->start_conf), 59 pcTableAssoc(p->table_assoc), 60 pcTableSets(p->table_sets), 61 useMasterId(p->use_master_id), 62 degree(p->degree) 63{ 64 // Don't consult stride prefetcher on instruction accesses 65 onInst = false; 66 67 assert(isPowerOf2(pcTableSets)); 68 69 for (int c = 0; c < maxContexts; c++) { 70 pcTable[c] = new StrideEntry*[pcTableSets]; 71 for (int s = 0; s < pcTableSets; s++) { 72 pcTable[c][s] = new StrideEntry[pcTableAssoc]; 73 } 74 } 75} 76 77StridePrefetcher::~StridePrefetcher() 78{ 79 for (int c = 0; c < maxContexts; c++) { 80 for (int s = 0; s < pcTableSets; s++) { 81 delete[] pcTable[c][s]; 82 } 83 } 84} 85 86void 87StridePrefetcher::calculatePrefetch(const PacketPtr &pkt, 88 std::vector<Addr> &addresses) 89{ 90 if (!pkt->req->hasPC()) { 91 DPRINTF(HWPrefetch, "Ignoring request with no PC.\n"); 92 return; 93 } 94 95 // Get required packet info 96 Addr pkt_addr = pkt->getAddr(); 97 Addr pc = pkt->req->getPC(); 98 bool is_secure = pkt->isSecure(); 99 MasterID master_id = useMasterId ? pkt->req->masterId() : 0; 100 101 assert(master_id < maxContexts); 102 103 // Lookup pc-based information 104 StrideEntry *entry; 105 106 if(pcTableHit(pc, is_secure, master_id, entry)) { 107 // Hit in table 108 int new_stride = pkt_addr - entry->lastAddr; 109 bool stride_match = (new_stride == entry->stride); 110 111 // Adjust confidence for stride entry 112 if (stride_match && new_stride != 0) { 113 if (entry->confidence < maxConf) 114 entry->confidence++; 115 } else { 116 if (entry->confidence > minConf) 117 entry->confidence--; 118 // If confidence has dropped below the threshold, train new stride 119 if (entry->confidence < threshConf) 120 entry->stride = new_stride; 121 } 122 123 DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), " 124 "conf %d\n", pc, pkt_addr, is_secure ? "s" : "ns", new_stride, 125 stride_match ? "match" : "change", 126 entry->confidence); 127 128 entry->lastAddr = pkt_addr; 129 130 // Abort prefetch generation if below confidence threshold 131 if (entry->confidence < threshConf) 132 return; 133 134 // Generate up to degree prefetches 135 for (int d = 1; d <= degree; d++) { 136 // Round strides up to atleast 1 cacheline 137 int prefetch_stride = new_stride; 138 if (abs(new_stride) < blkSize) { 139 prefetch_stride = (new_stride < 0) ? -blkSize : blkSize; 140 } 141 142 Addr new_addr = pkt_addr + d * prefetch_stride; 143 if (samePage(pkt_addr, new_addr)) { 144 DPRINTF(HWPrefetch, "Queuing prefetch to %#x.\n", new_addr); 145 addresses.push_back(new_addr); 146 } else { 147 // Record the number of page crossing prefetches generated 148 pfSpanPage += degree - d + 1; 149 DPRINTF(HWPrefetch, "Ignoring page crossing prefetch.\n"); 150 return; 151 } 152 } 153 } else { 154 // Miss in table 155 DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pkt_addr, 156 is_secure ? "s" : "ns"); 157 158 StrideEntry* entry = pcTableVictim(pc, master_id); 159 entry->instAddr = pc; 160 entry->lastAddr = pkt_addr; 161 entry->isSecure= is_secure; 162 entry->stride = 0; 163 entry->confidence = startConf; 164 } 165} 166 167inline Addr 168StridePrefetcher::pcHash(Addr pc) const 169{ 170 Addr hash1 = pc >> 1; 171 Addr hash2 = hash1 >> floorLog2(pcTableSets); 172 return (hash1 ^ hash2) & (Addr)(pcTableSets - 1); 173} 174 175inline StridePrefetcher::StrideEntry* 176StridePrefetcher::pcTableVictim(Addr pc, int master_id) 177{ 178 // Rand replacement for now 179 int set = pcHash(pc); 180 int way = random_mt.random<int>(0, pcTableAssoc - 1); 181 182 DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n", set, way); 183 return &pcTable[master_id][set][way]; 184} 185 186inline bool 187StridePrefetcher::pcTableHit(Addr pc, bool is_secure, int master_id, 188 StrideEntry* &entry) 189{ 190 int set = pcHash(pc); 191 StrideEntry* set_entries = pcTable[master_id][set]; 192 for (int way = 0; way < pcTableAssoc; way++) { 193 // Search ways for match 194 if (set_entries[way].instAddr == pc && 195 set_entries[way].isSecure == is_secure) { 196 DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way); 197 entry = &set_entries[way]; 198 return true; 199 } 200 } 201 return false; 202} 203 204StridePrefetcher* 205StridePrefetcherParams::create() 206{ 207 return new StridePrefetcher(this); 208} 209