[patch 081/108] x86: Set cpu_llc_id on AMD CPUs

Greg KH
2009-07-01T01:10:35Z

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2.6.30-stable review patch. If anyone has any objections, please let us know.

------------------

From: Andreas Herrmann <andreas.herrmann3@amd.com>

commit 99bd0c0fc4b04da54cb311953ef9489931c19c63 upstream.

This counts when building sched domains in case NUMA information
is not available.

( See cpu_coregroup_mask() which uses llc_shared_map which in turn is
created based on cpu_llc_id. )

Currently Linux builds domains as follows:
(example from a dual socket quad-core system)

CPU0 attaching sched-domain:
domain 0: span 0-7 level CPU
groups: 0 1 2 3 4 5 6 7

...

CPU7 attaching sched-domain:
domain 0: span 0-7 level CPU
groups: 7 0 1 2 3 4 5 6

Ever since that is borked for multi-core AMD CPU systems.
This patch fixes that and now we get a proper:

CPU0 attaching sched-domain:
domain 0: span 0-3 level MC
groups: 0 1 2 3
domain 1: span 0-7 level CPU
groups: 0-3 4-7

...

CPU7 attaching sched-domain:
domain 0: span 4-7 level MC
groups: 7 4 5 6
domain 1: span 0-7 level CPU
groups: 4-7 0-3

This allows scheduler to assign tasks to cores on different sockets
(i.e. that don't share last level cache) for performance reasons.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
LKML-Reference: <20090619085909.GJ5218@alberich.amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/kernel/cpu/amd.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -258,13 +258,15 @@ static void __cpuinit amd_detect_cmp(str
{
#ifdef CONFIG_X86_HT
unsigned bits;
+ int cpu = smp_processor_id();

bits = c->x86_coreid_bits;
-
/* Low order bits define the core id (index of core in socket) */
c->cpu_core_id = c->initial_apicid & ((1 << bits)-1);
/* Convert the initial APIC ID into the socket ID */
c->phys_proc_id = c->initial_apicid >> bits;
+ /* use socket ID also for last level cache */
+ per_cpu(cpu_llc_id, cpu) = c->phys_proc_id;
#endif
}