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.
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-ker...@vger.kernel.org>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Anton Blanchard <an...@ozlabs.org>
Cc: Oliver O'Halloran <ooh...@gmail.com>
Cc: Nathan Lynch <nath...@linux.ibm.com>
Cc: Michael Neuling <mi...@neuling.org>
Cc: Gautham R Shenoy <e...@linux.vnet.ibm.com>
Cc: Satheesh Rajendran <sathn...@linux.vnet.ibm.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Valentin Schneider <valentin.schnei...@arm.com>
Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
---
arch/powerpc/include/asm/smp.h | 5 -----
arch/powerpc/kernel/smp.c | 33 +++++++--------------------------
2 files changed, 7 insertions(+), 31 deletions(-)
diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 5bdc17a7049f..cf6e7c7be62b 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -119,11 +119,6 @@ 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);
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 95f0bf72e283..8c28e1b4957b 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -957,12 +957,17 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
local_memory_node(numa_cpu_lookup_table[cpu]));
}
#endif
+ /*
+ * cpu_core_map is no 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));
@@ -1251,9 +1256,7 @@ 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)
@@ -1303,7 +1306,6 @@ 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;
/*
@@ -1311,7 +1313,6 @@ 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))
@@ -1333,26 +1334,6 @@ 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. */
--
2.17.1
