queued.cc revision 11793:ef606668d247
1/* 2 * Copyright (c) 2014-2015 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 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions are 16 * met: redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer; 18 * redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution; 21 * neither the name of the copyright holders nor the names of its 22 * contributors may be used to endorse or promote products derived from 23 * this software without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 * 37 * Authors: Mitch Hayenga 38 */ 39 40#include "mem/cache/prefetch/queued.hh" 41 42#include "debug/HWPrefetch.hh" 43#include "mem/cache/base.hh" 44 45QueuedPrefetcher::QueuedPrefetcher(const QueuedPrefetcherParams *p) 46 : BasePrefetcher(p), queueSize(p->queue_size), latency(p->latency), 47 queueSquash(p->queue_squash), queueFilter(p->queue_filter), 48 cacheSnoop(p->cache_snoop), tagPrefetch(p->tag_prefetch) 49{ 50 51} 52 53QueuedPrefetcher::~QueuedPrefetcher() 54{ 55 // Delete the queued prefetch packets 56 for (DeferredPacket &p : pfq) { 57 delete p.pkt->req; 58 delete p.pkt; 59 } 60} 61 62Tick 63QueuedPrefetcher::notify(const PacketPtr &pkt) 64{ 65 // Verify this access type is observed by prefetcher 66 if (observeAccess(pkt)) { 67 Addr blk_addr = pkt->getBlockAddr(blkSize); 68 bool is_secure = pkt->isSecure(); 69 70 // Squash queued prefetches if demand miss to same line 71 if (queueSquash) { 72 auto itr = pfq.begin(); 73 while (itr != pfq.end()) { 74 if (itr->pkt->getAddr() == blk_addr && 75 itr->pkt->isSecure() == is_secure) { 76 delete itr->pkt->req; 77 delete itr->pkt; 78 itr = pfq.erase(itr); 79 } else { 80 ++itr; 81 } 82 } 83 } 84 85 // Calculate prefetches given this access 86 std::vector<AddrPriority> addresses; 87 calculatePrefetch(pkt, addresses); 88 89 // Queue up generated prefetches 90 for (AddrPriority& pf_info : addresses) { 91 92 // Block align prefetch address 93 pf_info.first &= ~(Addr)(blkSize - 1); 94 95 pfIdentified++; 96 DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, " 97 "inserting into prefetch queue.\n", pf_info.first); 98 99 // Create and insert the request 100 PacketPtr pf_pkt = insert(pf_info, is_secure); 101 102 if (pf_pkt != nullptr) { 103 if (tagPrefetch && pkt->req->hasPC()) { 104 // Tag prefetch packet with accessing pc 105 pf_pkt->req->setPC(pkt->req->getPC()); 106 } 107 } 108 } 109 } 110 111 return pfq.empty() ? MaxTick : pfq.front().tick; 112} 113 114PacketPtr 115QueuedPrefetcher::getPacket() 116{ 117 DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n"); 118 119 if (pfq.empty()) { 120 DPRINTF(HWPrefetch, "No hardware prefetches available.\n"); 121 return nullptr; 122 } 123 124 PacketPtr pkt = pfq.begin()->pkt; 125 pfq.pop_front(); 126 127 pfIssued++; 128 assert(pkt != nullptr); 129 DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr()); 130 return pkt; 131} 132 133std::list<QueuedPrefetcher::DeferredPacket>::const_iterator 134QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const 135{ 136 for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) { 137 if ((*dp).pkt->getAddr() == address && 138 (*dp).pkt->isSecure() == is_secure) return dp; 139 } 140 141 return pfq.end(); 142} 143 144QueuedPrefetcher::iterator 145QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) 146{ 147 for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) { 148 if (dp->pkt->getAddr() == address && 149 dp->pkt->isSecure() == is_secure) return dp; 150 } 151 152 return pfq.end(); 153} 154 155void 156QueuedPrefetcher::regStats() 157{ 158 BasePrefetcher::regStats(); 159 160 pfIdentified 161 .name(name() + ".pfIdentified") 162 .desc("number of prefetch candidates identified"); 163 164 pfBufferHit 165 .name(name() + ".pfBufferHit") 166 .desc("number of redundant prefetches already in prefetch queue"); 167 168 pfInCache 169 .name(name() + ".pfInCache") 170 .desc("number of redundant prefetches already in cache/mshr dropped"); 171 172 pfRemovedFull 173 .name(name() + ".pfRemovedFull") 174 .desc("number of prefetches dropped due to prefetch queue size"); 175 176 pfSpanPage 177 .name(name() + ".pfSpanPage") 178 .desc("number of prefetches not generated due to page crossing"); 179} 180 181PacketPtr 182QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure) 183{ 184 if (queueFilter) { 185 iterator it = inPrefetch(pf_info.first, is_secure); 186 /* If the address is already in the queue, update priority and leave */ 187 if (it != pfq.end()) { 188 pfBufferHit++; 189 if (it->priority < pf_info.second) { 190 /* Update priority value and position in the queue */ 191 it->priority = pf_info.second; 192 iterator prev = it; 193 bool cont = true; 194 while (cont && prev != pfq.begin()) { 195 prev--; 196 /* If the packet has higher priority, swap */ 197 if (*it > *prev) { 198 std::swap(*it, *prev); 199 it = prev; 200 } 201 } 202 DPRINTF(HWPrefetch, "Prefetch addr already in " 203 "prefetch queue, priority updated\n"); 204 } else { 205 DPRINTF(HWPrefetch, "Prefetch addr already in " 206 "prefetch queue\n"); 207 } 208 return nullptr; 209 } 210 } 211 212 if (cacheSnoop && (inCache(pf_info.first, is_secure) || 213 inMissQueue(pf_info.first, is_secure))) { 214 pfInCache++; 215 DPRINTF(HWPrefetch, "Dropping redundant in " 216 "cache/MSHR prefetch addr:%#x\n", pf_info.first); 217 return nullptr; 218 } 219 220 /* Create a prefetch memory request */ 221 Request *pf_req = 222 new Request(pf_info.first, blkSize, 0, masterId); 223 224 if (is_secure) { 225 pf_req->setFlags(Request::SECURE); 226 } 227 pf_req->taskId(ContextSwitchTaskId::Prefetcher); 228 PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq); 229 pf_pkt->allocate(); 230 231 /* Verify prefetch buffer space for request */ 232 if (pfq.size() == queueSize) { 233 pfRemovedFull++; 234 /* Lowest priority packet */ 235 iterator it = pfq.end(); 236 panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!"); 237 --it; 238 /* Look for oldest in that level of priority */ 239 panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!"); 240 iterator prev = it; 241 bool cont = true; 242 /* While not at the head of the queue */ 243 while (cont && prev != pfq.begin()) { 244 prev--; 245 /* While at the same level of priority */ 246 cont = (*prev).priority == (*it).priority; 247 if (cont) 248 /* update pointer */ 249 it = prev; 250 } 251 DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority " 252 "oldest packet, addr: %#x", it->pkt->getAddr()); 253 delete it->pkt->req; 254 delete it->pkt; 255 pfq.erase(it); 256 } 257 258 Tick pf_time = curTick() + clockPeriod() * latency; 259 DPRINTF(HWPrefetch, "Prefetch queued. " 260 "addr:%#x priority: %3d tick:%lld.\n", 261 pf_info.first, pf_info.second, pf_time); 262 263 /* Create the packet and find the spot to insert it */ 264 DeferredPacket dpp(pf_time, pf_pkt, pf_info.second); 265 if (pfq.size() == 0) { 266 pfq.emplace_back(dpp); 267 } else { 268 iterator it = pfq.end(); 269 while (it != pfq.begin() && dpp > *it) 270 --it; 271 /* If we reach the head, we have to see if the new element is new head 272 * or not */ 273 if (it == pfq.begin() && dpp <= *it) 274 it++; 275 pfq.insert(it, dpp); 276 } 277 278 return pf_pkt; 279} 280