refscale: Add SRCU-fast-updown readers

This commit adds refscale readers based on srcu_read_lock_fast_updown()
and srcu_read_unlock_fast_updown()
("refscale.scale_type=srcu-fast-updown"). On my x86 laptop, these are
about 2.2ns per pair.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index ece77f6d055b855cdd5a483bfea3e987e5165c40..65c04dfdab22720d70d734633c558a6dfdf71a41 100644 (file)
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -185,6 +185,7 @@ static const struct ref_scale_ops rcu_ops = {
 // Definitions for SRCU ref scale testing.
 DEFINE_STATIC_SRCU(srcu_refctl_scale);
 DEFINE_STATIC_SRCU_FAST(srcu_fast_refctl_scale);
+DEFINE_STATIC_SRCU_FAST_UPDOWN(srcu_fast_updown_refctl_scale);
 static struct srcu_struct *srcu_ctlp = &srcu_refctl_scale;
 
 static void srcu_ref_scale_read_section(const int nloops)
@@ -253,6 +254,42 @@ static const struct ref_scale_ops srcu_fast_ops = {
        .name           = "srcu-fast"
 };
 
+static bool srcu_fast_updown_sync_scale_init(void)
+{
+       srcu_ctlp = &srcu_fast_updown_refctl_scale;
+       return true;
+}
+
+static void srcu_fast_updown_ref_scale_read_section(const int nloops)
+{
+       int i;
+       struct srcu_ctr __percpu *scp;
+
+       for (i = nloops; i >= 0; i--) {
+               scp = srcu_read_lock_fast_updown(srcu_ctlp);
+               srcu_read_unlock_fast_updown(srcu_ctlp, scp);
+       }
+}
+
+static void srcu_fast_updown_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
+{
+       int i;
+       struct srcu_ctr __percpu *scp;
+
+       for (i = nloops; i >= 0; i--) {
+               scp = srcu_read_lock_fast_updown(srcu_ctlp);
+               un_delay(udl, ndl);
+               srcu_read_unlock_fast_updown(srcu_ctlp, scp);
+       }
+}
+
+static const struct ref_scale_ops srcu_fast_updown_ops = {
+       .init           = srcu_fast_updown_sync_scale_init,
+       .readsection    = srcu_fast_updown_ref_scale_read_section,
+       .delaysection   = srcu_fast_updown_ref_scale_delay_section,
+       .name           = "srcu-fast-updown"
+};
+
 #ifdef CONFIG_TASKS_RCU
 
 // Definitions for RCU Tasks ref scale testing: Empty read markers.
@@ -1170,7 +1207,8 @@ ref_scale_init(void)
        long i;
        int firsterr = 0;
        static const struct ref_scale_ops *scale_ops[] = {
-               &rcu_ops, &srcu_ops, &srcu_fast_ops, RCU_TRACE_OPS RCU_TASKS_OPS
+               &rcu_ops, &srcu_ops, &srcu_fast_ops, &srcu_fast_updown_ops,
+               RCU_TRACE_OPS RCU_TASKS_OPS
                &refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops,
                &acqrel_ops, &sched_clock_ops, &clock_ops, &jiffies_ops,
                &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,