crypto: iaa - Optimize rebalance_wq_table()

The function opencodes for_each_cpu() by using a plain for-loop. The
loop calls cpumask_weight() inside the conditional section. Because
cpumask_weight() is O(1), the overall complexity of the function is
O(node * node_cpus^2). Also, cpumask_nth() internally calls hweight(),
which, if not hardware accelerated, is slower than cpumask_next() in
for_each_cpu().

If switched to the dedicated for_each_cpu(), the rebalance_wq_table()
can drop calling cpumask_weight(), together with some housekeeping code.
This makes the overall complexity O(node * node_cpus), or simply speaking
O(nr_cpu_ids).

While there, fix opencoded for_each_possible_cpu() too.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/intel/iaa/iaa_crypto_main.c b/drivers/crypto/intel/iaa/iaa_crypto_main.c
index e9c762124f1104473626698530cb2b88e357f850..23f585219fb4b2c6777d51036baf19012901eb70 100644 (file)
--- a/drivers/crypto/intel/iaa/iaa_crypto_main.c
+++ b/drivers/crypto/intel/iaa/iaa_crypto_main.c
@@ -894,7 +894,7 @@ out:
 static void rebalance_wq_table(void)
 {
        const struct cpumask *node_cpus;
-       int node, cpu, iaa = -1;
+       int node_cpu, node, cpu, iaa = 0;
 
        if (nr_iaa == 0)
                return;
@@ -905,36 +905,29 @@ static void rebalance_wq_table(void)
        clear_wq_table();
 
        if (nr_iaa == 1) {
-               for (cpu = 0; cpu < nr_cpus; cpu++) {
-                       if (WARN_ON(wq_table_add_wqs(0, cpu))) {
-                               pr_debug("could not add any wqs for iaa 0 to cpu %d!\n", cpu);
-                               return;
-                       }
+               for_each_possible_cpu(cpu) {
+                       if (WARN_ON(wq_table_add_wqs(0, cpu)))
+                               goto err;
                }
 
                return;
        }
 
        for_each_node_with_cpus(node) {
+               cpu = 0;
                node_cpus = cpumask_of_node(node);
 
-               for (cpu = 0; cpu <  cpumask_weight(node_cpus); cpu++) {
-                       int node_cpu = cpumask_nth(cpu, node_cpus);
-
-                       if (WARN_ON(node_cpu >= nr_cpu_ids)) {
-                               pr_debug("node_cpu %d doesn't exist!\n", node_cpu);
-                               return;
-                       }
-
-                       if ((cpu % cpus_per_iaa) == 0)
-                               iaa++;
-
-                       if (WARN_ON(wq_table_add_wqs(iaa, node_cpu))) {
-                               pr_debug("could not add any wqs for iaa %d to cpu %d!\n", iaa, cpu);
-                               return;
-                       }
+               for_each_cpu(node_cpu, node_cpus) {
+                       iaa = cpu / cpus_per_iaa;
+                       if (WARN_ON(wq_table_add_wqs(iaa, node_cpu)))
+                               goto err;
+                       cpu++;
                }
        }
+
+       return;
+err:
+       pr_debug("could not add any wqs for iaa %d to cpu %d!\n", iaa, cpu);
 }
 
 static inline int check_completion(struct device *dev,