[Artful][PATCH 07/12] powerpc/perf/imc: Fix nest events on muti socket system

[Gustavo Walbon]

From: Anju T <anju at linux.vnet.ibm.com>

BugLink: https://bugs.launchpad.net/bugs/1481347

In a multi node system with discontiguous node ids, nest event values
are not showing up properly. eg. lscpu output:

  NUMA node0 CPU(s): 0-15
  NUMA node8 CPU(s): 16-31

Nest event values on such systems can be counted on CPUs <= 15:

  $./perf stat -e 'nest_powerbus0_imc/PM_PB_CYC/' -C 0-14 -I 1000 sleep 1000
  #           time             counts unit events
       1.000294577    30,17,24,42,880 nest_powerbus0_imc/PM_PB_CYC/

But not on CPUs >= 16:

  $./perf stat -e 'nest_powerbus0_imc/PM_PB_CYC/' -C 16-28 -I 1000 sleep 1000
  #           time             counts unit events
       1.000049902    <not supported> nest_powerbus0_imc/PM_PB_CYC/

This is because, when fetching the reference count, the node id (which
may be sparse) is used as the array index, not the node number (which
is 0 based and contiguous).

Fix it by using the node number as the array index.

  $./perf stat -e 'nest_powerbus0_imc/PM_PB_CYC/' -C 16-28 -I 1000 sleep 1000
  #           time             counts unit events
       1.000241961    26,12,35,28,704 nest_powerbus0_imc/PM_PB_CYC/

Signed-off-by: Anju T Sudhakar <anju at linux.vnet.ibm.com>
[mpe: Change log tweaks for clarity and brevity]
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
(cherry-picked from 7efbae90892b7858f1d4873d34ffffbeb460ed8b)
Signed-off-by: Gustavo Walbon <gwalbon at linux.vnet.ibm.com>
---
 arch/powerpc/perf/imc-pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index 52017f6eafd9..a8f95f96d54b 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -1064,7 +1064,7 @@ static int init_nest_pmu_ref(void)
 	 */
 	for_each_possible_cpu(cpu) {
 		nid = cpu_to_node(cpu);
-		for_each_online_node(i) {
+		for (i = 0; i < num_possible_nodes(); i++) {
 			if (nest_imc_refc[i].id == nid) {
 				per_cpu(local_nest_imc_refc, cpu) = &nest_imc_refc[i];
 				break;
-- 
2.13.3