stride.cc revision 13423
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), 69 degree(p->degree), 70 pcTable(pcTableAssoc, pcTableSets, name()) 71{ 72 assert(isPowerOf2(pcTableSets)); 73} 74 75StridePrefetcher::StrideEntry** 76StridePrefetcher::PCTable::allocateNewContext(int context) 77{ 78 auto res = entries.insert(std::make_pair(context, 79 new StrideEntry*[pcTableSets])); 80 auto it = res.first; 81 chatty_assert(res.second, "Allocating an already created context\n"); 82 assert(it->first == context); 83 84 DPRINTF(HWPrefetch, "Adding context %i with stride entries at %p\n", 85 context, it->second); 86 87 StrideEntry** entry = it->second; 88 for (int s = 0; s < pcTableSets; s++) { 89 entry[s] = new StrideEntry[pcTableAssoc]; 90 } 91 return entry; 92} 93 94StridePrefetcher::PCTable::~PCTable() { 95 for (auto entry : entries) { 96 for (int s = 0; s < pcTableSets; s++) { 97 delete[] entry.second[s]; 98 } 99 delete[] entry.second; 100 } 101} 102 103void 104StridePrefetcher::calculatePrefetch(const PacketPtr &pkt, 105 std::vector<AddrPriority> &addresses) 106{ 107 if (!pkt->req->hasPC()) { 108 DPRINTF(HWPrefetch, "Ignoring request with no PC.\n"); 109 return; 110 } 111 112 // Get required packet info 113 Addr pkt_addr = pkt->getAddr(); 114 Addr pc = pkt->req->getPC(); 115 bool is_secure = pkt->isSecure(); 116 MasterID master_id = useMasterId ? pkt->req->masterId() : 0; 117 118 // Search for entry in the pc table 119 StrideEntry *entry = findEntry(pc, is_secure, master_id); 120 121 if (entry != nullptr) { 122 // Hit in table 123 int new_stride = pkt_addr - entry->lastAddr; 124 bool stride_match = (new_stride == entry->stride); 125 126 // Adjust confidence for stride entry 127 if (stride_match && new_stride != 0) { 128 if (entry->confidence < maxConf) 129 entry->confidence++; 130 } else { 131 if (entry->confidence > minConf) 132 entry->confidence--; 133 // If confidence has dropped below the threshold, train new stride 134 if (entry->confidence < threshConf) 135 entry->stride = new_stride; 136 } 137 138 DPRINTF(HWPrefetch, "Hit: PC %x pkt_addr %x (%s) stride %d (%s), " 139 "conf %d\n", pc, pkt_addr, is_secure ? "s" : "ns", new_stride, 140 stride_match ? "match" : "change", 141 entry->confidence); 142 143 entry->lastAddr = pkt_addr; 144 145 // Abort prefetch generation if below confidence threshold 146 if (entry->confidence < threshConf) 147 return; 148 149 // Generate up to degree prefetches 150 for (int d = 1; d <= degree; d++) { 151 // Round strides up to atleast 1 cacheline 152 int prefetch_stride = new_stride; 153 if (abs(new_stride) < blkSize) { 154 prefetch_stride = (new_stride < 0) ? -blkSize : blkSize; 155 } 156 157 Addr new_addr = pkt_addr + d * prefetch_stride; 158 if (samePage(pkt_addr, new_addr)) { 159 DPRINTF(HWPrefetch, "Queuing prefetch to %#x.\n", new_addr); 160 addresses.push_back(AddrPriority(new_addr, 0)); 161 } else { 162 // Record the number of page crossing prefetches generated 163 pfSpanPage += degree - d + 1; 164 DPRINTF(HWPrefetch, "Ignoring page crossing prefetch.\n"); 165 return; 166 } 167 } 168 } else { 169 // Miss in table 170 DPRINTF(HWPrefetch, "Miss: PC %x pkt_addr %x (%s)\n", pc, pkt_addr, 171 is_secure ? "s" : "ns"); 172 173 StrideEntry* entry = pcTableVictim(pc, master_id); 174 entry->instAddr = pc; 175 entry->lastAddr = pkt_addr; 176 entry->isSecure= is_secure; 177 entry->stride = 0; 178 entry->confidence = startConf; 179 } 180} 181 182inline Addr 183StridePrefetcher::pcHash(Addr pc) const 184{ 185 Addr hash1 = pc >> 1; 186 Addr hash2 = hash1 >> floorLog2(pcTableSets); 187 return (hash1 ^ hash2) & (Addr)(pcTableSets - 1); 188} 189 190inline StridePrefetcher::StrideEntry* 191StridePrefetcher::pcTableVictim(Addr pc, int master_id) 192{ 193 // Rand replacement for now 194 int set = pcHash(pc); 195 int way = random_mt.random<int>(0, pcTableAssoc - 1); 196 197 DPRINTF(HWPrefetch, "Victimizing lookup table[%d][%d].\n", set, way); 198 return &pcTable[master_id][set][way]; 199} 200 201inline StridePrefetcher::StrideEntry* 202StridePrefetcher::findEntry(Addr pc, bool is_secure, int master_id) 203{ 204 int set = pcHash(pc); 205 StrideEntry* set_entries = pcTable[master_id][set]; 206 for (int way = 0; way < pcTableAssoc; way++) { 207 StrideEntry* entry = &set_entries[way]; 208 // Search ways for match 209 if ((entry->instAddr == pc) && (entry->isSecure == is_secure)) { 210 DPRINTF(HWPrefetch, "Lookup hit table[%d][%d].\n", set, way); 211 return entry; 212 } 213 } 214 return nullptr; 215} 216 217StridePrefetcher* 218StridePrefetcherParams::create() 219{ 220 return new StridePrefetcher(this); 221} 222