refscale: Add a "jiffies" test

This commit adds a "jiffies" test to refscale, allowing use of jiffies
to be compared to ktime_get_real_fast_ns().  On my x86 laptop, jiffies
is more than 20x faster.  (Though for many uses, the tens-of-nanoseconds
overhead of ktime_get_real_fast_ns() will be just fine.)

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 71d138573856f66f78ebcb938b9848bb01e5ee56..91a0fd0d4d9ab800a7238f88263090929b2422bf 100644 (file)
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -528,6 +528,38 @@ static struct ref_scale_ops clock_ops = {
        .name           = "clock"
 };
 
+static void ref_jiffies_section(const int nloops)
+{
+       u64 x = 0;
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--)
+               x += jiffies;
+       preempt_enable();
+       stopopts = x;
+}
+
+static void ref_jiffies_delay_section(const int nloops, const int udl, const int ndl)
+{
+       u64 x = 0;
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--) {
+               x += jiffies;
+               un_delay(udl, ndl);
+       }
+       preempt_enable();
+       stopopts = x;
+}
+
+static struct ref_scale_ops jiffies_ops = {
+       .readsection    = ref_jiffies_section,
+       .delaysection   = ref_jiffies_delay_section,
+       .name           = "jiffies"
+};
+
 ////////////////////////////////////////////////////////////////////////
 //
 // Methods leveraging SLAB_TYPESAFE_BY_RCU.
@@ -1047,7 +1079,7 @@ ref_scale_init(void)
        int firsterr = 0;
        static struct ref_scale_ops *scale_ops[] = {
                &rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops,
-               &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops,
+               &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, &jiffies_ops,
                &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
        };