Commit-ID: 5a925b4282d7f805deafde62001a83dbaf8be275
Gitweb: http://git.kernel.org/tip/5a925b4282d7f805deafde62001a83dbaf8be275
Author: Andreas Herrmann <andreas.herrmann3@xxxxxxx>
AuthorDate: Thu, 3 Sep 2009 09:44:28 +0200
Committer: H. Peter Anvin <hpa@xxxxxxxxx>
CommitDate: Thu, 3 Sep 2009 15:10:14 -0700
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 <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Andreas Herrmann <andreas.herrmann3@xxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
---
arch/x86/kernel/smpboot.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2fecda6..c36cc14 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;
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|