From bd4f901c778e9e3180a60b71a5680eb6724fd637 Mon Sep 17 00:00:00 2001 From: Mitch Hayenga Date: Tue, 23 Dec 2014 09:31:18 -0500 Subject: [PATCH] mem: Fix event scheduling issue for prefetches The cache's MemSidePacketQueue schedules a sendEvent based upon nextMSHRReadyTime() which is the time when the next MSHR is ready or whenever a future prefetch is ready. However, a prefetch being ready does not guarentee that it can obtain an MSHR. So, when all MSHRs are full, the simulation ends up unnecessiciarly scheduling a sendEvent every picosecond until an MSHR is finally freed and the prefetch can happen. This patch fixes this by not signaling the prefetch ready time if the prefetch could not be generated. The event is rescheduled as soon as a MSHR becomes available. --- src/mem/cache/cache_impl.hh | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/src/mem/cache/cache_impl.hh b/src/mem/cache/cache_impl.hh index 115e7aeb8..cb02f7558 100644 --- a/src/mem/cache/cache_impl.hh +++ b/src/mem/cache/cache_impl.hh @@ -1197,6 +1197,15 @@ Cache::recvTimingResp(PacketPtr pkt) if (wasFull && !mq->isFull()) { clearBlocked((BlockedCause)mq->index); } + + // Request the bus for a prefetch if this deallocation freed enough + // MSHRs for a prefetch to take place + if (prefetcher && mq == &mshrQueue && mshrQueue.canPrefetch()) { + Tick next_pf_time = std::max(prefetcher->nextPrefetchReadyTime(), + curTick()); + if (next_pf_time != MaxTick) + requestMemSideBus(Request_PF, next_pf_time); + } } // copy writebacks to write buffer @@ -1955,7 +1964,9 @@ Cache::nextMSHRReadyTime() const Tick nextReady = std::min(mshrQueue.nextMSHRReadyTime(), writeBuffer.nextMSHRReadyTime()); - if (prefetcher) { + // Don't signal prefetch ready time if no MSHRs available + // Will signal once enoguh MSHRs are deallocated + if (prefetcher && mshrQueue.canPrefetch()) { nextReady = std::min(nextReady, prefetcher->nextPrefetchReadyTime()); } -- 2.30.2