diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/mem/cache/mshr.cc | 83 |
1 files changed, 56 insertions, 27 deletions
diff --git a/src/mem/cache/mshr.cc b/src/mem/cache/mshr.cc index fa21f5cfc..d89adef19 100644 --- a/src/mem/cache/mshr.cc +++ b/src/mem/cache/mshr.cc @@ -318,16 +318,24 @@ MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order, // - there are other targets already deferred // - there's a pending invalidate to be applied after the response // comes back (but before this target is processed) + // - the MSHR's first (and only) non-deferred target is a cache + // maintenance packet + // - the new target is a cache maintenance packet (this is probably + // overly conservative but certainly safe) // - this target requires a writable block and either we're not // getting a writable block back or we have already snooped // another read request that will downgrade our writable block // to non-writable (Shared or Owned) - if (inService && - (!deferredTargets.empty() || hasPostInvalidate() || - (pkt->needsWritable() && - (!isPendingModified() || hasPostDowngrade() || isForward)))) { + PacketPtr tgt_pkt = targets.front().pkt; + if (pkt->req->isCacheMaintenance() || + tgt_pkt->req->isCacheMaintenance() || + !deferredTargets.empty() || + (inService && + (hasPostInvalidate() || + (pkt->needsWritable() && + (!isPendingModified() || hasPostDowngrade() || isForward))))) { // need to put on deferred list - if (hasPostInvalidate()) + if (inService && hasPostInvalidate()) replaceUpgrade(pkt); deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true, alloc_on_fill); @@ -349,7 +357,8 @@ MSHR::handleSnoop(PacketPtr pkt, Counter _order) // when we snoop packets the needsWritable and isInvalidate flags // should always be the same, however, this assumes that we never // snoop writes as they are currently not marked as invalidations - panic_if(pkt->needsWritable() != pkt->isInvalidate(), + panic_if((pkt->needsWritable() != pkt->isInvalidate()) && + !pkt->req->isCacheMaintenance(), "%s got snoop %s where needsWritable, " "does not match isInvalidate", name(), pkt->print()); @@ -367,7 +376,7 @@ MSHR::handleSnoop(PacketPtr pkt, Counter _order) // That is, even though the upper-level cache got out on its // local bus first, some other invalidating transaction // reached the global bus before the upgrade did. - if (pkt->needsWritable()) { + if (pkt->needsWritable() || pkt->req->isCacheInvalidate()) { targets.replaceUpgrades(); deferredTargets.replaceUpgrades(); } @@ -377,16 +386,18 @@ MSHR::handleSnoop(PacketPtr pkt, Counter _order) // From here on down, the request issued by this MSHR logically // precedes the request we're snooping. - if (pkt->needsWritable()) { + if (pkt->needsWritable() || pkt->req->isCacheInvalidate()) { // snooped request still precedes the re-request we'll have to // issue for deferred targets, if any... deferredTargets.replaceUpgrades(); } - if (hasPostInvalidate()) { - // a prior snoop has already appended an invalidation, so - // logically we don't have the block anymore; no need for - // further snooping. + PacketPtr tgt_pkt = targets.front().pkt; + if (hasPostInvalidate() || tgt_pkt->req->isCacheInvalidate()) { + // a prior snoop has already appended an invalidation or a + // cache invalidation operation is in progress, so logically + // we don't have the block anymore; no need for further + // snooping. return true; } @@ -401,7 +412,8 @@ MSHR::handleSnoop(PacketPtr pkt, Counter _order) // Start by determining if we will eventually respond or not, // matching the conditions checked in Cache::handleSnoop - bool will_respond = isPendingModified() && pkt->needsResponse(); + bool will_respond = isPendingModified() && pkt->needsResponse() && + !pkt->isClean(); // The packet we are snooping may be deleted by the time we // actually process the target, and we consequently need to @@ -435,10 +447,14 @@ MSHR::handleSnoop(PacketPtr pkt, Counter _order) targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, downstreamPending && targets.needsWritable, false); - if (pkt->needsWritable()) { + if (pkt->needsWritable() || pkt->isInvalidate()) { // This transaction will take away our pending copy postInvalidate = true; } + + if (pkt->isClean()) { + pkt->setSatisfied(); + } } if (!pkt->needsWritable() && !pkt->req->isUncacheable()) { @@ -490,23 +506,36 @@ MSHR::extractServiceableTargets(PacketPtr pkt) bool MSHR::promoteDeferredTargets() { - if (targets.empty()) { - if (deferredTargets.empty()) { - return false; - } + if (targets.empty() && deferredTargets.empty()) { + // nothing to promote + return false; + } - std::swap(targets, deferredTargets); + // the deferred targets can be generally promoted unless they + // contain a cache maintenance request + + // find the first target that is a cache maintenance request + auto it = std::find_if(deferredTargets.begin(), deferredTargets.end(), + [](MSHR::Target &t) { + return t.pkt->req->isCacheMaintenance(); + }); + if (it == deferredTargets.begin()) { + // if the first deferred target is a cache maintenance packet + // then we can promote provided the targets list is empty and + // we can service it on its own + if (targets.empty()) { + targets.splice(targets.end(), deferredTargets, it); + } } else { - // If the targets list is not empty then we have one targets - // from the deferredTargets list to the targets list. A new - // request will then service the targets list. - targets.splice(targets.end(), deferredTargets); - targets.populateFlags(); + // if a cache maintenance operation exists, we promote all the + // deferred targets that precede it, or all deferred targets + // otherwise + targets.splice(targets.end(), deferredTargets, + deferredTargets.begin(), it); } - // clear deferredTargets flags - deferredTargets.resetFlags(); - + deferredTargets.populateFlags(); + targets.populateFlags(); order = targets.front().order; readyTime = std::max(curTick(), targets.front().readyTime); |