For each cpu in cpumask, checks if it's running a lockless pagetable
walk. Then, run serialize_against_pte_lookup() only on these cpus.
serialize_agains_pte_lookup() can take a long while when there are a
lot of cpus in cpumask.
This method is intended to reduce this waiting, while not impacting
too much on the lockless pagetable walk.
Signed-off-by: Leonardo Bras <leonardo@xxxxxxxxxxxxx>
---
arch/powerpc/mm/book3s64/pgtable.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index bb138b628f86..4822ff1aac4b 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c
@@ -96,8 +96,22 @@ static DEFINE_PER_CPU(int, lockless_pgtbl_walk_counter);
*/
void serialize_against_pte_lookup(struct mm_struct *mm)
{
+ int cpu;
+ struct cpumask cm;
+
smp_mb();
- smp_call_function_many(mm_cpumask(mm), do_nothing, NULL, 1);
+
+ /*
+ * Fills a new cpumask only with cpus that are currently doing a
+ * lockless pagetable walk. This reduces time spent in this function.
+ */
+ cpumask_clear(&cm);
+ for_each_cpu(cpu, mm_cpumask((mm))) {
+ if (per_cpu(lockless_pgtbl_walk_counter, cpu) > 0)
+ cpumask_set_cpu(cpu, &cm);
+ }
+
+ smp_call_function_many(&cm, do_nothing, NULL, 1);
}
/* begin_lockless_pgtbl_walk: Must be inserted before a function call that does
--
2.24.1
