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/commit.hh | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'src/cpu/o3/commit.hh') diff --git a/src/cpu/o3/commit.hh b/src/cpu/o3/commit.hh index 473e5e51d..4c9ccf1eb 100644 --- a/src/cpu/o3/commit.hh +++ b/src/cpu/o3/commit.hh @@ -1,5 +1,5 @@ /* - * Copyright (c) 2010-2012 ARM Limited + * Copyright (c) 2010-2012, 2014 ARM Limited * All rights reserved. * * The license below extends only to copyright in the software and shall @@ -218,6 +218,9 @@ class DefaultCommit /** Takes over from another CPU's thread. */ void takeOverFrom(); + /** Deschedules a thread from scheduling */ + void deactivateThread(ThreadID tid); + /** Ticks the commit stage, which tries to commit instructions. */ void tick(); -- cgit v1.2.3