mshr.cc revision 11490:e03a6233d061
1/* 2 * Copyright (c) 2012-2013, 2015-2016 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) 2002-2005 The Regents of The University of Michigan 15 * Copyright (c) 2010 Advanced Micro Devices, Inc. 16 * All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions are 20 * met: redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer; 22 * redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution; 25 * neither the name of the copyright holders nor the names of its 26 * contributors may be used to endorse or promote products derived from 27 * this software without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 40 * 41 * Authors: Erik Hallnor 42 * Dave Greene 43 */ 44 45/** 46 * @file 47 * Miss Status and Handling Register (MSHR) definitions. 48 */ 49 50#include "mem/cache/mshr.hh" 51 52#include <algorithm> 53#include <cassert> 54#include <string> 55#include <vector> 56 57#include "base/misc.hh" 58#include "base/types.hh" 59#include "debug/Cache.hh" 60#include "mem/cache/cache.hh" 61#include "sim/core.hh" 62 63using namespace std; 64 65MSHR::MSHR() : downstreamPending(false), 66 pendingModified(false), 67 postInvalidate(false), postDowngrade(false), 68 isForward(false), allocOnFill(false) 69{ 70} 71 72MSHR::TargetList::TargetList() 73 : needsWritable(false), hasUpgrade(false) 74{} 75 76 77inline void 78MSHR::TargetList::add(PacketPtr pkt, Tick readyTime, 79 Counter order, Target::Source source, bool markPending) 80{ 81 if (source != Target::FromSnoop) { 82 if (pkt->needsWritable()) { 83 needsWritable = true; 84 } 85 86 // StoreCondReq is effectively an upgrade if it's in an MSHR 87 // since it would have been failed already if we didn't have a 88 // read-only copy 89 if (pkt->isUpgrade() || pkt->cmd == MemCmd::StoreCondReq) { 90 hasUpgrade = true; 91 } 92 } 93 94 if (markPending) { 95 // Iterate over the SenderState stack and see if we find 96 // an MSHR entry. If we do, set the downstreamPending 97 // flag. Otherwise, do nothing. 98 MSHR *mshr = pkt->findNextSenderState<MSHR>(); 99 if (mshr != nullptr) { 100 assert(!mshr->downstreamPending); 101 mshr->downstreamPending = true; 102 } else { 103 // No need to clear downstreamPending later 104 markPending = false; 105 } 106 } 107 108 emplace_back(pkt, readyTime, order, source, markPending); 109} 110 111 112static void 113replaceUpgrade(PacketPtr pkt) 114{ 115 // remember if the current packet has data allocated 116 bool has_data = pkt->hasData() || pkt->hasRespData(); 117 118 if (pkt->cmd == MemCmd::UpgradeReq) { 119 pkt->cmd = MemCmd::ReadExReq; 120 DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n"); 121 } else if (pkt->cmd == MemCmd::SCUpgradeReq) { 122 pkt->cmd = MemCmd::SCUpgradeFailReq; 123 DPRINTF(Cache, "Replacing SCUpgradeReq with SCUpgradeFailReq\n"); 124 } else if (pkt->cmd == MemCmd::StoreCondReq) { 125 pkt->cmd = MemCmd::StoreCondFailReq; 126 DPRINTF(Cache, "Replacing StoreCondReq with StoreCondFailReq\n"); 127 } 128 129 if (!has_data) { 130 // there is no sensible way of setting the data field if the 131 // new command actually would carry data 132 assert(!pkt->hasData()); 133 134 if (pkt->hasRespData()) { 135 // we went from a packet that had no data (neither request, 136 // nor response), to one that does, and therefore we need to 137 // actually allocate space for the data payload 138 pkt->allocate(); 139 } 140 } 141} 142 143 144void 145MSHR::TargetList::replaceUpgrades() 146{ 147 if (!hasUpgrade) 148 return; 149 150 for (auto& t : *this) { 151 replaceUpgrade(t.pkt); 152 } 153 154 hasUpgrade = false; 155} 156 157 158void 159MSHR::TargetList::clearDownstreamPending() 160{ 161 for (auto& t : *this) { 162 if (t.markedPending) { 163 // Iterate over the SenderState stack and see if we find 164 // an MSHR entry. If we find one, clear the 165 // downstreamPending flag by calling 166 // clearDownstreamPending(). This recursively clears the 167 // downstreamPending flag in all caches this packet has 168 // passed through. 169 MSHR *mshr = t.pkt->findNextSenderState<MSHR>(); 170 if (mshr != nullptr) { 171 mshr->clearDownstreamPending(); 172 } 173 } 174 } 175} 176 177 178bool 179MSHR::TargetList::checkFunctional(PacketPtr pkt) 180{ 181 for (auto& t : *this) { 182 if (pkt->checkFunctional(t.pkt)) { 183 return true; 184 } 185 } 186 187 return false; 188} 189 190 191void 192MSHR::TargetList::print(std::ostream &os, int verbosity, 193 const std::string &prefix) const 194{ 195 for (auto& t : *this) { 196 const char *s; 197 switch (t.source) { 198 case Target::FromCPU: 199 s = "FromCPU"; 200 break; 201 case Target::FromSnoop: 202 s = "FromSnoop"; 203 break; 204 case Target::FromPrefetcher: 205 s = "FromPrefetcher"; 206 break; 207 default: 208 s = ""; 209 break; 210 } 211 ccprintf(os, "%s%s: ", prefix, s); 212 t.pkt->print(os, verbosity, ""); 213 } 214} 215 216 217void 218MSHR::allocate(Addr blk_addr, unsigned blk_size, PacketPtr target, 219 Tick when_ready, Counter _order, bool alloc_on_fill) 220{ 221 blkAddr = blk_addr; 222 blkSize = blk_size; 223 isSecure = target->isSecure(); 224 readyTime = when_ready; 225 order = _order; 226 assert(target); 227 isForward = false; 228 allocOnFill = alloc_on_fill; 229 _isUncacheable = target->req->isUncacheable(); 230 inService = false; 231 downstreamPending = false; 232 assert(targets.isReset()); 233 // Don't know of a case where we would allocate a new MSHR for a 234 // snoop (mem-side request), so set source according to request here 235 Target::Source source = (target->cmd == MemCmd::HardPFReq) ? 236 Target::FromPrefetcher : Target::FromCPU; 237 targets.add(target, when_ready, _order, source, true); 238 assert(deferredTargets.isReset()); 239} 240 241 242void 243MSHR::clearDownstreamPending() 244{ 245 assert(downstreamPending); 246 downstreamPending = false; 247 // recursively clear flag on any MSHRs we will be forwarding 248 // responses to 249 targets.clearDownstreamPending(); 250} 251 252void 253MSHR::markInService(bool pending_modified_resp) 254{ 255 assert(!inService); 256 257 inService = true; 258 pendingModified = targets.needsWritable || pending_modified_resp; 259 postInvalidate = postDowngrade = false; 260 261 if (!downstreamPending) { 262 // let upstream caches know that the request has made it to a 263 // level where it's going to get a response 264 targets.clearDownstreamPending(); 265 } 266} 267 268 269void 270MSHR::deallocate() 271{ 272 assert(targets.empty()); 273 targets.resetFlags(); 274 assert(deferredTargets.isReset()); 275 inService = false; 276} 277 278/* 279 * Adds a target to an MSHR 280 */ 281void 282MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order, 283 bool alloc_on_fill) 284{ 285 // assume we'd never issue a prefetch when we've got an 286 // outstanding miss 287 assert(pkt->cmd != MemCmd::HardPFReq); 288 289 // uncacheable accesses always allocate a new MSHR, and cacheable 290 // accesses ignore any uncacheable MSHRs, thus we should never 291 // have targets addded if originally allocated uncacheable 292 assert(!_isUncacheable); 293 294 // potentially re-evaluate whether we should allocate on a fill or 295 // not 296 allocOnFill = allocOnFill || alloc_on_fill; 297 298 // if there's a request already in service for this MSHR, we will 299 // have to defer the new target until after the response if any of 300 // the following are true: 301 // - there are other targets already deferred 302 // - there's a pending invalidate to be applied after the response 303 // comes back (but before this target is processed) 304 // - this target requires a writable block and either we're not 305 // getting a writable block back or we have already snooped 306 // another read request that will downgrade our writable block 307 // to non-writable (Shared or Owned) 308 if (inService && 309 (!deferredTargets.empty() || hasPostInvalidate() || 310 (pkt->needsWritable() && 311 (!isPendingModified() || hasPostDowngrade() || isForward)))) { 312 // need to put on deferred list 313 if (hasPostInvalidate()) 314 replaceUpgrade(pkt); 315 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true); 316 } else { 317 // No request outstanding, or still OK to append to 318 // outstanding request: append to regular target list. Only 319 // mark pending if current request hasn't been issued yet 320 // (isn't in service). 321 targets.add(pkt, whenReady, _order, Target::FromCPU, !inService); 322 } 323} 324 325bool 326MSHR::handleSnoop(PacketPtr pkt, Counter _order) 327{ 328 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 329 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 330 331 // when we snoop packets the needsWritable and isInvalidate flags 332 // should always be the same, however, this assumes that we never 333 // snoop writes as they are currently not marked as invalidations 334 panic_if(pkt->needsWritable() != pkt->isInvalidate(), 335 "%s got snoop %s to addr %#llx where needsWritable, " 336 "does not match isInvalidate", name(), pkt->cmdString(), 337 pkt->getAddr()); 338 339 if (!inService || (pkt->isExpressSnoop() && downstreamPending)) { 340 // Request has not been issued yet, or it's been issued 341 // locally but is buffered unissued at some downstream cache 342 // which is forwarding us this snoop. Either way, the packet 343 // we're snooping logically precedes this MSHR's request, so 344 // the snoop has no impact on the MSHR, but must be processed 345 // in the standard way by the cache. The only exception is 346 // that if we're an L2+ cache buffering an UpgradeReq from a 347 // higher-level cache, and the snoop is invalidating, then our 348 // buffered upgrades must be converted to read exclusives, 349 // since the upper-level cache no longer has a valid copy. 350 // That is, even though the upper-level cache got out on its 351 // local bus first, some other invalidating transaction 352 // reached the global bus before the upgrade did. 353 if (pkt->needsWritable()) { 354 targets.replaceUpgrades(); 355 deferredTargets.replaceUpgrades(); 356 } 357 358 return false; 359 } 360 361 // From here on down, the request issued by this MSHR logically 362 // precedes the request we're snooping. 363 if (pkt->needsWritable()) { 364 // snooped request still precedes the re-request we'll have to 365 // issue for deferred targets, if any... 366 deferredTargets.replaceUpgrades(); 367 } 368 369 if (hasPostInvalidate()) { 370 // a prior snoop has already appended an invalidation, so 371 // logically we don't have the block anymore; no need for 372 // further snooping. 373 return true; 374 } 375 376 if (isPendingModified() || pkt->isInvalidate()) { 377 // We need to save and replay the packet in two cases: 378 // 1. We're awaiting a writable copy (Modified or Exclusive), 379 // so this MSHR is the orgering point, and we need to respond 380 // after we receive data. 381 // 2. It's an invalidation (e.g., UpgradeReq), and we need 382 // to forward the snoop up the hierarchy after the current 383 // transaction completes. 384 385 // Start by determining if we will eventually respond or not, 386 // matching the conditions checked in Cache::handleSnoop 387 bool will_respond = isPendingModified() && pkt->needsResponse() && 388 pkt->cmd != MemCmd::InvalidateReq; 389 390 // The packet we are snooping may be deleted by the time we 391 // actually process the target, and we consequently need to 392 // save a copy here. Clear flags and also allocate new data as 393 // the original packet data storage may have been deleted by 394 // the time we get to process this packet. In the cases where 395 // we are not responding after handling the snoop we also need 396 // to create a copy of the request to be on the safe side. In 397 // the latter case the cache is responsible for deleting both 398 // the packet and the request as part of handling the deferred 399 // snoop. 400 PacketPtr cp_pkt = will_respond ? new Packet(pkt, true, true) : 401 new Packet(new Request(*pkt->req), pkt->cmd); 402 403 if (will_respond) { 404 // we are the ordering point, and will consequently 405 // respond, and depending on whether the packet 406 // needsWritable or not we either pass a Shared line or a 407 // Modified line 408 pkt->setCacheResponding(); 409 410 // inform the cache hierarchy that this cache had the line 411 // in the Modified state, even if the response is passed 412 // as Shared (and thus non-writable) 413 pkt->setResponderHadWritable(); 414 415 // in the case of an uncacheable request there is no need 416 // to set the responderHadWritable flag, but since the 417 // recipient does not care there is no harm in doing so 418 } 419 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, 420 downstreamPending && targets.needsWritable); 421 422 if (pkt->needsWritable()) { 423 // This transaction will take away our pending copy 424 postInvalidate = true; 425 } 426 } 427 428 if (!pkt->needsWritable() && !pkt->req->isUncacheable()) { 429 // This transaction will get a read-shared copy, downgrading 430 // our copy if we had a writable one 431 postDowngrade = true; 432 // make sure that any downstream cache does not respond with a 433 // writable (and dirty) copy even if it has one, unless it was 434 // explicitly asked for one 435 pkt->setHasSharers(); 436 } 437 438 return true; 439} 440 441 442bool 443MSHR::promoteDeferredTargets() 444{ 445 assert(targets.empty()); 446 if (deferredTargets.empty()) { 447 return false; 448 } 449 450 // swap targets & deferredTargets lists 451 std::swap(targets, deferredTargets); 452 453 // clear deferredTargets flags 454 deferredTargets.resetFlags(); 455 456 order = targets.front().order; 457 readyTime = std::max(curTick(), targets.front().readyTime); 458 459 return true; 460} 461 462 463void 464MSHR::promoteWritable() 465{ 466 if (deferredTargets.needsWritable && 467 !(hasPostInvalidate() || hasPostDowngrade())) { 468 // We got a writable response, but we have deferred targets 469 // which are waiting to request a writable copy (not because 470 // of a pending invalidate). This can happen if the original 471 // request was for a read-only block, but we got a writable 472 // response anyway. Since we got the writable copy there's no 473 // need to defer the targets, so move them up to the regular 474 // target list. 475 assert(!targets.needsWritable); 476 targets.needsWritable = true; 477 // if any of the deferred targets were upper-level cache 478 // requests marked downstreamPending, need to clear that 479 assert(!downstreamPending); // not pending here anymore 480 deferredTargets.clearDownstreamPending(); 481 // this clears out deferredTargets too 482 targets.splice(targets.end(), deferredTargets); 483 deferredTargets.resetFlags(); 484 } 485} 486 487 488bool 489MSHR::checkFunctional(PacketPtr pkt) 490{ 491 // For printing, we treat the MSHR as a whole as single entity. 492 // For other requests, we iterate over the individual targets 493 // since that's where the actual data lies. 494 if (pkt->isPrint()) { 495 pkt->checkFunctional(this, blkAddr, isSecure, blkSize, nullptr); 496 return false; 497 } else { 498 return (targets.checkFunctional(pkt) || 499 deferredTargets.checkFunctional(pkt)); 500 } 501} 502 503bool 504MSHR::sendPacket(Cache &cache) 505{ 506 return cache.sendMSHRQueuePacket(this); 507} 508 509void 510MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const 511{ 512 ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n", 513 prefix, blkAddr, blkAddr + blkSize - 1, 514 isSecure ? "s" : "ns", 515 isForward ? "Forward" : "", 516 allocOnFill ? "AllocOnFill" : "", 517 needsWritable() ? "Wrtbl" : "", 518 _isUncacheable ? "Unc" : "", 519 inService ? "InSvc" : "", 520 downstreamPending ? "DwnPend" : "", 521 hasPostInvalidate() ? "PostInv" : "", 522 hasPostDowngrade() ? "PostDowngr" : ""); 523 524 ccprintf(os, "%s Targets:\n", prefix); 525 targets.print(os, verbosity, prefix + " "); 526 if (!deferredTargets.empty()) { 527 ccprintf(os, "%s Deferred Targets:\n", prefix); 528 deferredTargets.print(os, verbosity, prefix + " "); 529 } 530} 531 532std::string 533MSHR::print() const 534{ 535 ostringstream str; 536 print(str); 537 return str.str(); 538} 539