queued.cc revision 13551
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 <cassert> 43 44#include "base/logging.hh" 45#include "base/trace.hh" 46#include "debug/HWPrefetch.hh" 47#include "mem/request.hh" 48#include "params/QueuedPrefetcher.hh" 49 50QueuedPrefetcher::QueuedPrefetcher(const QueuedPrefetcherParams *p) 51 : BasePrefetcher(p), queueSize(p->queue_size), latency(p->latency), 52 queueSquash(p->queue_squash), queueFilter(p->queue_filter), 53 cacheSnoop(p->cache_snoop), tagPrefetch(p->tag_prefetch) 54{ 55 56} 57 58QueuedPrefetcher::~QueuedPrefetcher() 59{ 60 // Delete the queued prefetch packets 61 for (DeferredPacket &p : pfq) { 62 delete p.pkt; 63 } 64} 65 66void 67QueuedPrefetcher::notify(const PacketPtr &pkt, const PrefetchInfo &pfi) 68{ 69 Addr blk_addr = blockAddress(pfi.getAddr()); 70 bool is_secure = pfi.isSecure(); 71 72 // Squash queued prefetches if demand miss to same line 73 if (queueSquash) { 74 auto itr = pfq.begin(); 75 while (itr != pfq.end()) { 76 if (itr->pfInfo.getAddr() == blk_addr && 77 itr->pfInfo.isSecure() == is_secure) { 78 delete itr->pkt; 79 itr = pfq.erase(itr); 80 } else { 81 ++itr; 82 } 83 } 84 } 85 86 // Calculate prefetches given this access 87 std::vector<AddrPriority> addresses; 88 calculatePrefetch(pfi, addresses); 89 90 // Queue up generated prefetches 91 for (AddrPriority& addr_prio : addresses) { 92 93 // Block align prefetch address 94 addr_prio.first = blockAddress(addr_prio.first); 95 96 PrefetchInfo new_pfi(pfi,addr_prio.first); 97 98 pfIdentified++; 99 DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, " 100 "inserting into prefetch queue.\n", new_pfi.getAddr()); 101 102 // Create and insert the request 103 insert(pkt, new_pfi, addr_prio.second); 104 } 105} 106 107PacketPtr 108QueuedPrefetcher::getPacket() 109{ 110 DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n"); 111 112 if (pfq.empty()) { 113 DPRINTF(HWPrefetch, "No hardware prefetches available.\n"); 114 return nullptr; 115 } 116 117 PacketPtr pkt = pfq.front().pkt; 118 pfq.pop_front(); 119 120 pfIssued++; 121 assert(pkt != nullptr); 122 DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr()); 123 return pkt; 124} 125 126QueuedPrefetcher::const_iterator 127QueuedPrefetcher::inPrefetch(const PrefetchInfo &pfi) const 128{ 129 for (const_iterator dp = pfq.begin(); dp != pfq.end(); dp++) { 130 if (dp->pfInfo.sameAddr(pfi)) return dp; 131 } 132 133 return pfq.end(); 134} 135 136QueuedPrefetcher::iterator 137QueuedPrefetcher::inPrefetch(const PrefetchInfo &pfi) 138{ 139 for (iterator dp = pfq.begin(); dp != pfq.end(); dp++) { 140 if (dp->pfInfo.sameAddr(pfi)) return dp; 141 } 142 143 return pfq.end(); 144} 145 146void 147QueuedPrefetcher::regStats() 148{ 149 BasePrefetcher::regStats(); 150 151 pfIdentified 152 .name(name() + ".pfIdentified") 153 .desc("number of prefetch candidates identified"); 154 155 pfBufferHit 156 .name(name() + ".pfBufferHit") 157 .desc("number of redundant prefetches already in prefetch queue"); 158 159 pfInCache 160 .name(name() + ".pfInCache") 161 .desc("number of redundant prefetches already in cache/mshr dropped"); 162 163 pfRemovedFull 164 .name(name() + ".pfRemovedFull") 165 .desc("number of prefetches dropped due to prefetch queue size"); 166 167 pfSpanPage 168 .name(name() + ".pfSpanPage") 169 .desc("number of prefetches not generated due to page crossing"); 170} 171 172void 173QueuedPrefetcher::insert(const PacketPtr &pkt, PrefetchInfo &new_pfi, 174 int32_t priority) 175{ 176 if (queueFilter) { 177 iterator it = inPrefetch(new_pfi); 178 /* If the address is already in the queue, update priority and leave */ 179 if (it != pfq.end()) { 180 pfBufferHit++; 181 if (it->priority < priority) { 182 /* Update priority value and position in the queue */ 183 it->priority = priority; 184 iterator prev = it; 185 bool cont = true; 186 while (cont && prev != pfq.begin()) { 187 prev--; 188 /* If the packet has higher priority, swap */ 189 if (*it > *prev) { 190 std::swap(*it, *prev); 191 it = prev; 192 } 193 } 194 DPRINTF(HWPrefetch, "Prefetch addr already in " 195 "prefetch queue, priority updated\n"); 196 } else { 197 DPRINTF(HWPrefetch, "Prefetch addr already in " 198 "prefetch queue\n"); 199 } 200 return; 201 } 202 } 203 204 Addr target_addr = new_pfi.getAddr(); 205 if (useVirtualAddresses) { 206 assert(pkt->req->hasPaddr()); 207 //if we trained with virtual addresses, compute the phsysical address 208 if (new_pfi.getAddr() >= pkt->req->getVaddr()) { 209 //positive stride 210 target_addr = pkt->req->getPaddr() + 211 (new_pfi.getAddr() - pkt->req->getVaddr()); 212 } else { 213 //negative stride 214 target_addr = pkt->req->getPaddr() - 215 (pkt->req->getVaddr() - new_pfi.getAddr()); 216 } 217 } 218 219 if (cacheSnoop && (inCache(target_addr, new_pfi.isSecure()) || 220 inMissQueue(target_addr, new_pfi.isSecure()))) { 221 pfInCache++; 222 DPRINTF(HWPrefetch, "Dropping redundant in " 223 "cache/MSHR prefetch addr:%#x\n", target_addr); 224 return; 225 } 226 227 /* Create a prefetch memory request */ 228 RequestPtr pf_req = 229 std::make_shared<Request>(target_addr, blkSize, 0, masterId); 230 231 if (new_pfi.isSecure()) { 232 pf_req->setFlags(Request::SECURE); 233 } 234 pf_req->taskId(ContextSwitchTaskId::Prefetcher); 235 PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq); 236 pf_pkt->allocate(); 237 if (tagPrefetch && new_pfi.hasPC()) { 238 // Tag prefetch packet with accessing pc 239 pf_pkt->req->setPC(new_pfi.getPC()); 240 } 241 242 /* Verify prefetch buffer space for request */ 243 if (pfq.size() == queueSize) { 244 pfRemovedFull++; 245 /* Lowest priority packet */ 246 iterator it = pfq.end(); 247 panic_if (it == pfq.begin(), "Prefetch queue is both full and empty!"); 248 --it; 249 /* Look for oldest in that level of priority */ 250 panic_if (it == pfq.begin(), "Prefetch queue is full with 1 element!"); 251 iterator prev = it; 252 bool cont = true; 253 /* While not at the head of the queue */ 254 while (cont && prev != pfq.begin()) { 255 prev--; 256 /* While at the same level of priority */ 257 cont = prev->priority == it->priority; 258 if (cont) 259 /* update pointer */ 260 it = prev; 261 } 262 DPRINTF(HWPrefetch, "Prefetch queue full, removing lowest priority " 263 "oldest packet, addr: %#x", it->pfInfo.getAddr()); 264 delete it->pkt; 265 pfq.erase(it); 266 } 267 268 Tick pf_time = curTick() + clockPeriod() * latency; 269 DPRINTF(HWPrefetch, "Prefetch queued. " 270 "addr:%#x priority: %3d tick:%lld.\n", 271 target_addr, priority, pf_time); 272 273 /* Create the packet and find the spot to insert it */ 274 DeferredPacket dpp(new_pfi, pf_time, pf_pkt, priority); 275 if (pfq.size() == 0) { 276 pfq.emplace_back(dpp); 277 } else { 278 iterator it = pfq.end(); 279 do { 280 --it; 281 } while (it != pfq.begin() && dpp > *it); 282 /* If we reach the head, we have to see if the new element is new head 283 * or not */ 284 if (it == pfq.begin() && dpp <= *it) 285 it++; 286 pfq.insert(it, dpp); 287 } 288} 289