mshr.cc revision 11271:f4ad5be63ba8
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) 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 <algorithm> 51#include <cassert> 52#include <string> 53#include <vector> 54 55#include "base/misc.hh" 56#include "base/types.hh" 57#include "debug/Cache.hh" 58#include "mem/cache/cache.hh" 59#include "mem/cache/mshr.hh" 60#include "sim/core.hh" 61 62using namespace std; 63 64MSHR::MSHR() : readyTime(0), _isUncacheable(false), downstreamPending(false), 65 pendingDirty(false), 66 postInvalidate(false), postDowngrade(false), 67 queue(NULL), order(0), blkAddr(0), 68 blkSize(0), isSecure(false), inService(false), 69 isForward(false), allocOnFill(false), 70 threadNum(InvalidThreadID), data(NULL) 71{ 72} 73 74 75MSHR::TargetList::TargetList() 76 : needsExclusive(false), hasUpgrade(false) 77{} 78 79 80inline void 81MSHR::TargetList::add(PacketPtr pkt, Tick readyTime, 82 Counter order, Target::Source source, bool markPending) 83{ 84 if (source != Target::FromSnoop) { 85 if (pkt->needsExclusive()) { 86 needsExclusive = true; 87 } 88 89 // StoreCondReq is effectively an upgrade if it's in an MSHR 90 // since it would have been failed already if we didn't have a 91 // read-only copy 92 if (pkt->isUpgrade() || pkt->cmd == MemCmd::StoreCondReq) { 93 hasUpgrade = true; 94 } 95 } 96 97 if (markPending) { 98 // Iterate over the SenderState stack and see if we find 99 // an MSHR entry. If we do, set the downstreamPending 100 // flag. Otherwise, do nothing. 101 MSHR *mshr = pkt->findNextSenderState<MSHR>(); 102 if (mshr != NULL) { 103 assert(!mshr->downstreamPending); 104 mshr->downstreamPending = true; 105 } else { 106 // No need to clear downstreamPending later 107 markPending = false; 108 } 109 } 110 111 emplace_back(pkt, readyTime, order, source, markPending); 112} 113 114 115static void 116replaceUpgrade(PacketPtr pkt) 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} 129 130 131void 132MSHR::TargetList::replaceUpgrades() 133{ 134 if (!hasUpgrade) 135 return; 136 137 for (auto& t : *this) { 138 replaceUpgrade(t.pkt); 139 } 140 141 hasUpgrade = false; 142} 143 144 145void 146MSHR::TargetList::clearDownstreamPending() 147{ 148 for (auto& t : *this) { 149 if (t.markedPending) { 150 // Iterate over the SenderState stack and see if we find 151 // an MSHR entry. If we find one, clear the 152 // downstreamPending flag by calling 153 // clearDownstreamPending(). This recursively clears the 154 // downstreamPending flag in all caches this packet has 155 // passed through. 156 MSHR *mshr = t.pkt->findNextSenderState<MSHR>(); 157 if (mshr != NULL) { 158 mshr->clearDownstreamPending(); 159 } 160 } 161 } 162} 163 164 165bool 166MSHR::TargetList::checkFunctional(PacketPtr pkt) 167{ 168 for (auto& t : *this) { 169 if (pkt->checkFunctional(t.pkt)) { 170 return true; 171 } 172 } 173 174 return false; 175} 176 177 178void 179MSHR::TargetList::print(std::ostream &os, int verbosity, 180 const std::string &prefix) const 181{ 182 for (auto& t : *this) { 183 const char *s; 184 switch (t.source) { 185 case Target::FromCPU: 186 s = "FromCPU"; 187 break; 188 case Target::FromSnoop: 189 s = "FromSnoop"; 190 break; 191 case Target::FromPrefetcher: 192 s = "FromPrefetcher"; 193 break; 194 default: 195 s = ""; 196 break; 197 } 198 ccprintf(os, "%s%s: ", prefix, s); 199 t.pkt->print(os, verbosity, ""); 200 } 201} 202 203 204void 205MSHR::allocate(Addr blk_addr, unsigned blk_size, PacketPtr target, 206 Tick when_ready, Counter _order, bool alloc_on_fill) 207{ 208 blkAddr = blk_addr; 209 blkSize = blk_size; 210 isSecure = target->isSecure(); 211 readyTime = when_ready; 212 order = _order; 213 assert(target); 214 isForward = false; 215 allocOnFill = alloc_on_fill; 216 _isUncacheable = target->req->isUncacheable(); 217 inService = false; 218 downstreamPending = false; 219 threadNum = 0; 220 assert(targets.isReset()); 221 // Don't know of a case where we would allocate a new MSHR for a 222 // snoop (mem-side request), so set source according to request here 223 Target::Source source = (target->cmd == MemCmd::HardPFReq) ? 224 Target::FromPrefetcher : Target::FromCPU; 225 targets.add(target, when_ready, _order, source, true); 226 assert(deferredTargets.isReset()); 227 data = NULL; 228} 229 230 231void 232MSHR::clearDownstreamPending() 233{ 234 assert(downstreamPending); 235 downstreamPending = false; 236 // recursively clear flag on any MSHRs we will be forwarding 237 // responses to 238 targets.clearDownstreamPending(); 239} 240 241bool 242MSHR::markInService(bool pending_dirty_resp) 243{ 244 assert(!inService); 245 if (isForwardNoResponse()) { 246 // we just forwarded the request packet & don't expect a 247 // response, so get rid of it 248 assert(getNumTargets() == 1); 249 popTarget(); 250 return true; 251 } 252 253 inService = true; 254 pendingDirty = targets.needsExclusive || pending_dirty_resp; 255 postInvalidate = postDowngrade = false; 256 257 if (!downstreamPending) { 258 // let upstream caches know that the request has made it to a 259 // level where it's going to get a response 260 targets.clearDownstreamPending(); 261 } 262 return false; 263} 264 265 266void 267MSHR::deallocate() 268{ 269 assert(targets.empty()); 270 targets.resetFlags(); 271 assert(deferredTargets.isReset()); 272 inService = false; 273} 274 275/* 276 * Adds a target to an MSHR 277 */ 278void 279MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order, 280 bool alloc_on_fill) 281{ 282 // assume we'd never issue a prefetch when we've got an 283 // outstanding miss 284 assert(pkt->cmd != MemCmd::HardPFReq); 285 286 // uncacheable accesses always allocate a new MSHR, and cacheable 287 // accesses ignore any uncacheable MSHRs, thus we should never 288 // have targets addded if originally allocated uncacheable 289 assert(!_isUncacheable); 290 291 // potentially re-evaluate whether we should allocate on a fill or 292 // not 293 allocOnFill = allocOnFill || alloc_on_fill; 294 295 // if there's a request already in service for this MSHR, we will 296 // have to defer the new target until after the response if any of 297 // the following are true: 298 // - there are other targets already deferred 299 // - there's a pending invalidate to be applied after the response 300 // comes back (but before this target is processed) 301 // - this target requires an exclusive block and either we're not 302 // getting an exclusive block back or we have already snooped 303 // another read request that will downgrade our exclusive block 304 // to shared 305 if (inService && 306 (!deferredTargets.empty() || hasPostInvalidate() || 307 (pkt->needsExclusive() && 308 (!isPendingDirty() || hasPostDowngrade() || isForward)))) { 309 // need to put on deferred list 310 if (hasPostInvalidate()) 311 replaceUpgrade(pkt); 312 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true); 313 } else { 314 // No request outstanding, or still OK to append to 315 // outstanding request: append to regular target list. Only 316 // mark pending if current request hasn't been issued yet 317 // (isn't in service). 318 targets.add(pkt, whenReady, _order, Target::FromCPU, !inService); 319 } 320} 321 322bool 323MSHR::handleSnoop(PacketPtr pkt, Counter _order) 324{ 325 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 326 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 327 if (!inService || (pkt->isExpressSnoop() && downstreamPending)) { 328 // Request has not been issued yet, or it's been issued 329 // locally but is buffered unissued at some downstream cache 330 // which is forwarding us this snoop. Either way, the packet 331 // we're snooping logically precedes this MSHR's request, so 332 // the snoop has no impact on the MSHR, but must be processed 333 // in the standard way by the cache. The only exception is 334 // that if we're an L2+ cache buffering an UpgradeReq from a 335 // higher-level cache, and the snoop is invalidating, then our 336 // buffered upgrades must be converted to read exclusives, 337 // since the upper-level cache no longer has a valid copy. 338 // That is, even though the upper-level cache got out on its 339 // local bus first, some other invalidating transaction 340 // reached the global bus before the upgrade did. 341 if (pkt->needsExclusive()) { 342 targets.replaceUpgrades(); 343 deferredTargets.replaceUpgrades(); 344 } 345 346 return false; 347 } 348 349 // From here on down, the request issued by this MSHR logically 350 // precedes the request we're snooping. 351 if (pkt->needsExclusive()) { 352 // snooped request still precedes the re-request we'll have to 353 // issue for deferred targets, if any... 354 deferredTargets.replaceUpgrades(); 355 } 356 357 if (hasPostInvalidate()) { 358 // a prior snoop has already appended an invalidation, so 359 // logically we don't have the block anymore; no need for 360 // further snooping. 361 return true; 362 } 363 364 if (isPendingDirty() || pkt->isInvalidate()) { 365 // We need to save and replay the packet in two cases: 366 // 1. We're awaiting an exclusive copy, so ownership is pending, 367 // and we need to deal with the snoop after we receive data. 368 // 2. It's an invalidation (e.g., UpgradeReq), and we need 369 // to forward the snoop up the hierarchy after the current 370 // transaction completes. 371 372 // Start by determining if we will eventually respond or not, 373 // matching the conditions checked in Cache::handleSnoop 374 bool will_respond = isPendingDirty() && pkt->needsResponse() && 375 pkt->cmd != MemCmd::InvalidateReq; 376 377 // The packet we are snooping may be deleted by the time we 378 // actually process the target, and we consequently need to 379 // save a copy here. Clear flags and also allocate new data as 380 // the original packet data storage may have been deleted by 381 // the time we get to process this packet. In the cases where 382 // we are not responding after handling the snoop we also need 383 // to create a copy of the request to be on the safe side. In 384 // the latter case the cache is responsible for deleting both 385 // the packet and the request as part of handling the deferred 386 // snoop. 387 PacketPtr cp_pkt = will_respond ? new Packet(pkt, true, true) : 388 new Packet(new Request(*pkt->req), pkt->cmd); 389 390 if (isPendingDirty()) { 391 // The new packet will need to get the response from the 392 // MSHR already queued up here 393 pkt->assertMemInhibit(); 394 // in the case of an uncacheable request there is no need 395 // to set the exclusive flag, but since the recipient does 396 // not care there is no harm in doing so 397 pkt->setSupplyExclusive(); 398 } 399 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, 400 downstreamPending && targets.needsExclusive); 401 402 if (pkt->needsExclusive()) { 403 // This transaction will take away our pending copy 404 postInvalidate = true; 405 } 406 } 407 408 if (!pkt->needsExclusive() && !pkt->req->isUncacheable()) { 409 // This transaction will get a read-shared copy, downgrading 410 // our copy if we had an exclusive one 411 postDowngrade = true; 412 pkt->assertShared(); 413 } 414 415 return true; 416} 417 418 419bool 420MSHR::promoteDeferredTargets() 421{ 422 assert(targets.empty()); 423 if (deferredTargets.empty()) { 424 return false; 425 } 426 427 // swap targets & deferredTargets lists 428 std::swap(targets, deferredTargets); 429 430 // clear deferredTargets flags 431 deferredTargets.resetFlags(); 432 433 order = targets.front().order; 434 readyTime = std::max(curTick(), targets.front().readyTime); 435 436 return true; 437} 438 439 440void 441MSHR::promoteExclusive() 442{ 443 if (deferredTargets.needsExclusive && 444 !(hasPostInvalidate() || hasPostDowngrade())) { 445 // We got an exclusive response, but we have deferred targets 446 // which are waiting to request an exclusive copy (not because 447 // of a pending invalidate). This can happen if the original 448 // request was for a read-only (non-exclusive) block, but we 449 // got an exclusive copy anyway because of the E part of the 450 // MOESI/MESI protocol. Since we got the exclusive copy 451 // there's no need to defer the targets, so move them up to 452 // the regular target list. 453 assert(!targets.needsExclusive); 454 targets.needsExclusive = true; 455 // if any of the deferred targets were upper-level cache 456 // requests marked downstreamPending, need to clear that 457 assert(!downstreamPending); // not pending here anymore 458 deferredTargets.clearDownstreamPending(); 459 // this clears out deferredTargets too 460 targets.splice(targets.end(), deferredTargets); 461 deferredTargets.resetFlags(); 462 } 463} 464 465 466bool 467MSHR::checkFunctional(PacketPtr pkt) 468{ 469 // For printing, we treat the MSHR as a whole as single entity. 470 // For other requests, we iterate over the individual targets 471 // since that's where the actual data lies. 472 if (pkt->isPrint()) { 473 pkt->checkFunctional(this, blkAddr, isSecure, blkSize, NULL); 474 return false; 475 } else { 476 return (targets.checkFunctional(pkt) || 477 deferredTargets.checkFunctional(pkt)); 478 } 479} 480 481 482void 483MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const 484{ 485 ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n", 486 prefix, blkAddr, blkAddr + blkSize - 1, 487 isSecure ? "s" : "ns", 488 isForward ? "Forward" : "", 489 allocOnFill ? "AllocOnFill" : "", 490 isForwardNoResponse() ? "ForwNoResp" : "", 491 needsExclusive() ? "Excl" : "", 492 _isUncacheable ? "Unc" : "", 493 inService ? "InSvc" : "", 494 downstreamPending ? "DwnPend" : "", 495 hasPostInvalidate() ? "PostInv" : "", 496 hasPostDowngrade() ? "PostDowngr" : ""); 497 498 ccprintf(os, "%s Targets:\n", prefix); 499 targets.print(os, verbosity, prefix + " "); 500 if (!deferredTargets.empty()) { 501 ccprintf(os, "%s Deferred Targets:\n", prefix); 502 deferredTargets.print(os, verbosity, prefix + " "); 503 } 504} 505 506std::string 507MSHR::print() const 508{ 509 ostringstream str; 510 print(str); 511 return str.str(); 512} 513