diff options
| -rw-r--r-- | src/mem/cache/cache.hh | 3 | ||||
| -rw-r--r-- | src/mem/cache/cache_impl.hh | 28 | ||||
| -rw-r--r-- | src/mem/cache/miss/mshr.cc | 2 | ||||
| -rw-r--r-- | src/mem/packet.hh | 6 |
4 files changed, 26 insertions, 13 deletions
diff --git a/src/mem/cache/cache.hh b/src/mem/cache/cache.hh index 57028a05e..7dfe9e8f1 100644 --- a/src/mem/cache/cache.hh +++ b/src/mem/cache/cache.hh @@ -190,7 +190,8 @@ class Cache : public BaseCache * @param new_state The new coherence state for the block. */ void handleSnoop(PacketPtr ptk, BlkType *blk, - bool is_timing, bool is_deferred); + bool is_timing, bool is_deferred, + bool lower_mshr_pending); /** * Create a writeback request for the given block. diff --git a/src/mem/cache/cache_impl.hh b/src/mem/cache/cache_impl.hh index c8c1a239c..82410afe1 100644 --- a/src/mem/cache/cache_impl.hh +++ b/src/mem/cache/cache_impl.hh @@ -754,7 +754,7 @@ Cache<TagStore>::handleResponse(PacketPtr pkt) } else { // response to snoop request DPRINTF(Cache, "processing deferred snoop...\n"); - handleSnoop(target->pkt, blk, true, true); + handleSnoop(target->pkt, blk, true, true, false); } mshr->popTarget(); @@ -917,7 +917,8 @@ Cache<TagStore>::doTimingSupplyResponse(PacketPtr req_pkt, template<class TagStore> void Cache<TagStore>::handleSnoop(PacketPtr pkt, BlkType *blk, - bool is_timing, bool is_deferred) + bool is_timing, bool is_deferred, + bool lower_mshr_pending) { assert(pkt->isRequest()); @@ -929,8 +930,8 @@ Cache<TagStore>::handleSnoop(PacketPtr pkt, BlkType *blk, if (is_timing) { Packet *snoopPkt = new Packet(pkt, true); // clear flags snoopPkt->setExpressSnoop(); - if (is_deferred) { - snoopPkt->setDeferredSnoop(); + if (lower_mshr_pending) { + snoopPkt->setLowerMSHRPending(); } snoopPkt->senderState = new ForwardResponseRecord(pkt, this); cpuSidePort->sendTiming(snoopPkt); @@ -1017,8 +1018,19 @@ Cache<TagStore>::snoopTiming(PacketPtr pkt) Addr blk_addr = pkt->getAddr() & ~(Addr(blkSize-1)); MSHR *mshr = mshrQueue.findMatch(blk_addr); - // better not be snooping a request that conflicts with something - // we have outstanding... + + // If a lower cache has an operation on this block pending (not + // yet in service) on the MSHR, then the upper caches need to know + // about it, as this means that the pending operation logically + // succeeds the current snoop. It's not sufficient to record + // whether the MSHR *is* in service, as this misses the window + // where the lower cache has completed the request and the + // response is on its way back up the hierarchy. + bool lower_mshr_pending = + (mshr && (!mshr->inService) || pkt->lowerMSHRPending()); + + // Let the MSHR itself track the snoop and decide whether we want + // to go ahead and do the regular cache snoop if (mshr && mshr->handleSnoop(pkt, order++)) { DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %x\n", blk_addr); @@ -1063,7 +1075,7 @@ Cache<TagStore>::snoopTiming(PacketPtr pkt) } } - handleSnoop(pkt, blk, true, false); + handleSnoop(pkt, blk, true, false, lower_mshr_pending); } @@ -1078,7 +1090,7 @@ Cache<TagStore>::snoopAtomic(PacketPtr pkt) } BlkType *blk = tags->findBlock(pkt->getAddr()); - handleSnoop(pkt, blk, false, false); + handleSnoop(pkt, blk, false, false, false); return hitLatency; } diff --git a/src/mem/cache/miss/mshr.cc b/src/mem/cache/miss/mshr.cc index 856819c10..b9dfdf729 100644 --- a/src/mem/cache/miss/mshr.cc +++ b/src/mem/cache/miss/mshr.cc @@ -164,7 +164,7 @@ MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order) bool MSHR::handleSnoop(PacketPtr pkt, Counter _order) { - if (!inService || (pkt->isExpressSnoop() && !pkt->isDeferredSnoop())) { + if (!inService || (pkt->isExpressSnoop() && pkt->lowerMSHRPending())) { // Request has not been issued yet, or it's been issued // locally but is buffered unissued at some downstream cache // which is forwarding us this snoop. Either way, the packet diff --git a/src/mem/packet.hh b/src/mem/packet.hh index 8063c7ae7..779ea49a2 100644 --- a/src/mem/packet.hh +++ b/src/mem/packet.hh @@ -257,7 +257,7 @@ class Packet : public FastAlloc Shared, // Special control flags ExpressSnoop, - DeferredSnoop, + LowerMSHRPending, // not yet in service NUM_PACKET_FLAGS }; @@ -323,8 +323,8 @@ class Packet : public FastAlloc // Special control flags void setExpressSnoop() { flags[ExpressSnoop] = true; } bool isExpressSnoop() { return flags[ExpressSnoop]; } - void setDeferredSnoop() { flags[DeferredSnoop] = true; } - bool isDeferredSnoop() { return flags[DeferredSnoop]; } + void setLowerMSHRPending() { flags[LowerMSHRPending] = true; } + bool lowerMSHRPending() { return flags[LowerMSHRPending]; } // Network error conditions... encapsulate them as methods since // their encoding keeps changing (from result field to command |