From 5a925b4282d7f805deafde62001a83dbaf8be275 Mon Sep 17 00:00:00 2001 From: Andreas Herrmann Date: Thu, 3 Sep 2009 09:44:28 +0200 Subject: x86, sched: Workaround broken sched domain creation for AMD Magny-Cours Current sched domain creation code can't handle multi-node processors. When switching to power_savings scheduling errors show up and system might hang later on (due to broken sched domain hierarchy): # echo 0 >> /sys/devices/system/cpu/sched_mc_power_savings CPU0 attaching sched-domain: domain 0: span 0-5 level MC groups: 0 1 2 3 4 5 domain 1: span 0-23 level NODE groups: 0-5 6-11 18-23 12-17 ... # echo 1 >> /sys/devices/system/cpu/sched_mc_power_savings CPU0 attaching sched-domain: domain 0: span 0-11 level MC groups: 0 1 2 3 4 5 6 7 8 9 10 11 ERROR: parent span is not a superset of domain->span domain 1: span 0-5 level CPU ERROR: domain->groups does not contain CPU0 groups: 6-11 (__cpu_power = 12288) ERROR: groups don't span domain->span domain 2: span 0-23 level NODE groups: ERROR: domain->cpu_power not set ERROR: groups don't span domain->span ... Fixing all aspects of power-savings scheduling for Magny-Cours needs some larger changes in the sched domain creation code. As a short-term and temporary workaround avoid the problems by extending "the worst possible hack" ;-( and always use llc_shared_map on AMD Magny-Cours when MC domain span is calculated. With this I get: # echo 1 >> /sys/devices/system/cpu/sched_mc_power_savings CPU0 attaching sched-domain: domain 0: span 0-5 level MC groups: 0 1 2 3 4 5 domain 1: span 0-5 level CPU groups: 0-5 (__cpu_power = 6144) domain 2: span 0-23 level NODE groups: 0-5 (__cpu_power = 6144) 6-11 (__cpu_power = 6144) 18-23 (__cpu_power = 6144) 12-17 (__cpu_power = 6144) ... I.e. no errors during sched domain creation, no system hangs, and also mc_power_savings scheduling works to a certain extend. Cc: Peter Zijlstra Signed-off-by: Andreas Herrmann Signed-off-by: H. Peter Anvin --- arch/x86/kernel/smpboot.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel/smpboot.c') diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 2fecda69ee64..c36cc1452cdc 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -434,7 +434,8 @@ const struct cpumask *cpu_coregroup_mask(int cpu) * For perf, we return last level cache shared map. * And for power savings, we return cpu_core_map */ - if (sched_mc_power_savings || sched_smt_power_savings) + if ((sched_mc_power_savings || sched_smt_power_savings) && + !(cpu_has(c, X86_FEATURE_AMD_DCM))) return cpu_core_mask(cpu); else return c->llc_shared_map; -- cgit v1.2.3-59-g8ed1b