[RFC PATCH 3/8] shazptr: Add refscale test for wildcard

Boqun Feng
2025-04-14T06:01:24Z

Add the refscale test for shazptr, which starts another shazptr critical
section inside an existing one to measure the reader side performance
when wildcard logic is triggered.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
kernel/rcu/refscale.c | 40 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 154520e4ee4c..fdbb4a2c91fe 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -928,6 +928,44 @@ static const struct ref_scale_ops shazptr_ops = {
.name = "shazptr"
};

+static void ref_shazptr_wc_read_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ preempt_disable();
+ {
+ guard(shazptr)(ref_shazptr_read_section);
+ /* Trigger wildcard logic */
+ guard(shazptr)(ref_shazptr_wc_read_section);
+ }
+ preempt_enable();
+ }
+}
+
+static void ref_shazptr_wc_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ preempt_disable();
+ {
+ guard(shazptr)(ref_shazptr_delay_section);
+ /* Trigger wildcard logic */
+ guard(shazptr)(ref_shazptr_wc_delay_section);
+ un_delay(udl, ndl);
+ }
+ preempt_enable();
+ }
+}
+
+static const struct ref_scale_ops shazptr_wildcard_ops = {
+ .init = ref_shazptr_init,
+ .readsection = ref_shazptr_wc_read_section,
+ .delaysection = ref_shazptr_wc_delay_section,
+ .name = "shazptr_wildcard"
+};
+
static void rcu_scale_one_reader(void)
{
if (readdelay <= 0)
@@ -1235,7 +1273,7 @@ ref_scale_init(void)
&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,
- &shazptr_ops,
+ &shazptr_ops, &shazptr_wildcard_ops,
};

if (!torture_init_begin(scale_type, verbose))
--
2.47.1