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powerpc/smp: Stop updating cpu_core_mask 

Anton Blanchard reported that his 4096 vcpu KVM guest took around 30
minutes to boot. He also analyzed it to the time taken to iterate while
setting the cpu_core_mask.

Further analysis shows that cpu_core_mask and cpu_cpu_mask for any CPU
would be equal on Power. However updating cpu_core_mask took forever to
update as its a per cpu cpumask variable. Instead cpu_cpu_mask was a per
NODE /per DIE cpumask that was shared by all the respective CPUs.

Also cpu_cpu_mask is needed from a scheduler perspective. However
cpu_core_map is an exported symbol. Hence stop updating cpu_core_map
and make it point to cpu_cpu_mask.

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/20200921095653.9701-3-srikar@linux.vnet.ibm.com
This commit is contained in:
Srikar Dronamraju 2020-09-21 15:26:44 +05:30 committed by Michael Ellerman
parent 4bce545903
commit 4ca234a9cb
2 changed files with 7 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/powerpc/include/asm/smp.h
View File

@ -121,11 +121,6 @@ static inline struct cpumask *cpu_sibling_mask(int cpu)
return per_cpu(cpu_sibling_map, cpu);
}
static inline struct cpumask *cpu_core_mask(int cpu)
{
return per_cpu(cpu_core_map, cpu);
}
static inline struct cpumask *cpu_l2_cache_mask(int cpu)
{
return per_cpu(cpu_l2_cache_map, cpu);

33
arch/powerpc/kernel/smp.c
View File

@ -953,12 +953,17 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
local_memory_node(numa_cpu_lookup_table[cpu]));
}
#endif
/*
* cpu_core_map is now more updated and exists only since
* its been exported for long. It only will have a snapshot
* of cpu_cpu_mask.
*/
cpumask_copy(per_cpu(cpu_core_map, cpu), cpu_cpu_mask(cpu));
}
/* Init the cpumasks so the boot CPU is related to itself */
cpumask_set_cpu(boot_cpuid, cpu_sibling_mask(boot_cpuid));
cpumask_set_cpu(boot_cpuid, cpu_l2_cache_mask(boot_cpuid));
cpumask_set_cpu(boot_cpuid, cpu_core_mask(boot_cpuid));
if (has_coregroup_support())
cpumask_set_cpu(boot_cpuid, cpu_coregroup_mask(boot_cpuid));
@ -1260,9 +1265,7 @@ static void remove_cpu_from_masks(int cpu)
{
int i;
/* NB: cpu_core_mask is a superset of the others */
for_each_cpu(i, cpu_core_mask(cpu)) {
set_cpus_unrelated(cpu, i, cpu_core_mask);
for_each_cpu(i, cpu_cpu_mask(cpu)) {
set_cpus_unrelated(cpu, i, cpu_l2_cache_mask);
set_cpus_unrelated(cpu, i, cpu_sibling_mask);
if (has_big_cores)
@ -1312,7 +1315,6 @@ EXPORT_SYMBOL_GPL(get_physical_package_id);
static void add_cpu_to_masks(int cpu)
{
int first_thread = cpu_first_thread_sibling(cpu);
int pkg_id = get_physical_package_id(cpu);
int i;
/*
@ -1320,7 +1322,6 @@ static void add_cpu_to_masks(int cpu)
* add it to it's own thread sibling mask.
*/
cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
cpumask_set_cpu(cpu, cpu_core_mask(cpu));
for (i = first_thread; i < first_thread + threads_per_core; i++)
if (cpu_online(i))
@ -1342,26 +1343,6 @@ static void add_cpu_to_masks(int cpu)
set_cpus_related(cpu, i, cpu_coregroup_mask);
}
}
if (pkg_id == -1) {
struct cpumask *(*mask)(int) = cpu_sibling_mask;
/*
* Copy the sibling mask into core sibling mask and
* mark any CPUs on the same chip as this CPU.
*/
if (shared_caches)
mask = cpu_l2_cache_mask;
for_each_cpu(i, mask(cpu))
set_cpus_related(cpu, i, cpu_core_mask);
return;
}
for_each_cpu(i, cpu_online_mask)
if (get_physical_package_id(i) == pkg_id)
set_cpus_related(cpu, i, cpu_core_mask);
}
/* Activate a secondary processor. */