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authorMitch Hayenga <mitch.hayenga@arm.com>2014-12-23 09:31:18 -0500
committerMitch Hayenga <mitch.hayenga@arm.com>2014-12-23 09:31:18 -0500
commitbd4f901c778e9e3180a60b71a5680eb6724fd637 (patch)
tree059ddcc960962d505bf7ab95c9c52093ba0c05e3
parent4acd4a205525a79555f783767ab0d6a5f9c31eb5 (diff)
downloadgem5-bd4f901c778e9e3180a60b71a5680eb6724fd637.tar.xz
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.
-rw-r--r--src/mem/cache/cache_impl.hh13
1 files changed, 12 insertions, 1 deletions
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<TagStore>::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<TagStore>::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());
}