From 4f26bedc1883da58d1dceba2bbc555417b7a0cca Mon Sep 17 00:00:00 2001 From: Mitch Hayenga Date: Wed, 3 Sep 2014 07:42:37 -0400 Subject: cpu: Fix SMT scheduling issue with the O3 cpu The o3 cpu could attempt to schedule inactive threads under round-robin SMT mode. This is because it maintained an independent priority list of threads from the active thread list. This priority list could be come stale once threads were inactive, leading to the cpu trying to fetch/commit from inactive threads. Additionally the fetch queue is now forcibly flushed of instrctuctions from the de-scheduled thread. Relevant output: 24557000: system.cpu: [tid:1]: Calling deactivate thread. 24557000: system.cpu: [tid:1]: Removing from active threads list 24557500: system.cpu: FullO3CPU: Ticking main, FullO3CPU. 24557500: system.cpu.fetch: Running stage. 24557500: system.cpu.fetch: Attempting to fetch from [tid:1] --- src/cpu/o3/fetch.hh | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'src/cpu/o3/fetch.hh') diff --git a/src/cpu/o3/fetch.hh b/src/cpu/o3/fetch.hh index 2e9428ef1..4d01610d9 100644 --- a/src/cpu/o3/fetch.hh +++ b/src/cpu/o3/fetch.hh @@ -255,6 +255,8 @@ class DefaultFetch /** Tells fetch to wake up from a quiesce instruction. */ void wakeFromQuiesce(); + /** For priority-based fetch policies, need to keep update priorityList */ + void deactivateThread(ThreadID tid); private: /** Reset this pipeline stage */ void resetStage(); @@ -484,8 +486,8 @@ class DefaultFetch /** The size of the fetch queue in micro-ops */ unsigned fetchQueueSize; - /** Queue of fetched instructions */ - std::deque fetchQueue; + /** Queue of fetched instructions. Per-thread to prevent HoL blocking. */ + std::deque fetchQueue[Impl::MaxThreads]; /** Whether or not the fetch buffer data is valid. */ bool fetchBufferValid[Impl::MaxThreads]; -- cgit v1.2.3