From 70edd4a7c753ba18e3e4bb9e97b6d85156cea738 Mon Sep 17 00:00:00 2001
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Date: Mon, 21 Sep 2020 15:26:46 +0530
Subject: [PATCH] powerpc/smp: Optimize remove_cpu_from_masks
References: jsc#SLE-13615 bsc#1180100 ltc#190257
Patch-mainline: v5.10-rc1
Git-commit: 70edd4a7c753ba18e3e4bb9e97b6d85156cea738
While offlining a CPU, system currently iterate through all the CPUs in
the DIE to clear sibling, l2_cache and smallcore maps. However if there
are more cores in a DIE, system can end up spending more time iterating
through CPUs which are completely unrelated.
Optimize this by only iterating through smaller but relevant cpumap.
If shared_cache is set, cpu_l2_cache_map should be relevant else
cpu_sibling_map would be relevant.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Tested-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200921095653.9701-5-srikar@linux.vnet.ibm.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kernel/smp.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index aecc01f0e95e..9cdb966f00b3 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1263,14 +1263,21 @@ static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int))
#ifdef CONFIG_HOTPLUG_CPU
static void remove_cpu_from_masks(int cpu)
{
+ struct cpumask *(*mask_fn)(int) = cpu_sibling_mask;
int i;
- for_each_cpu(i, cpu_cpu_mask(cpu)) {
+ if (shared_caches)
+ mask_fn = cpu_l2_cache_mask;
+
+ for_each_cpu(i, mask_fn(cpu)) {
set_cpus_unrelated(cpu, i, cpu_l2_cache_mask);
set_cpus_unrelated(cpu, i, cpu_sibling_mask);
if (has_big_cores)
set_cpus_unrelated(cpu, i, cpu_smallcore_mask);
- if (has_coregroup_support())
+ }
+
+ if (has_coregroup_support()) {
+ for_each_cpu(i, cpu_coregroup_mask(cpu))
set_cpus_unrelated(cpu, i, cpu_coregroup_mask);
}
}
--
2.26.2