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powerpc/smp: Optimize remove_cpu_from_masks 

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
This commit is contained in:
Srikar Dronamraju 2020-09-21 15:26:46 +05:30 committed by Michael Ellerman
parent e29e9ed665
commit 70edd4a7c7
1 changed files with 9 additions and 2 deletions
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11
arch/powerpc/kernel/smp.c
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@ -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);
}
}