2023-07-17 18:24:52

by Paul E. McKenney

Subject: [PATCH rcu 0/3] Reference-side scalability test updates for v6.6

Hello!

This series contains reference-side scalability tests:

1. Add CONFIG_PREEMPT_DYNAMIC=n to NOPREEMPT scenario.

2. Fix uninitalized use of wait_queue_head_t, courtesy of Waiman
Long.

3. Add a "jiffies" test.

Thanx, Paul

------------------------------------------------------------------------

b/kernel/rcu/refscale.c | 3
b/tools/testing/selftests/rcutorture/configs/refscale/NOPREEMPT | 1
kernel/rcu/refscale.c | 34 +++++++++-
3 files changed, 35 insertions(+), 3 deletions(-)

2023-07-17 18:25:26

by Paul E. McKenney

Subject: [PATCH rcu 1/3] refscale: Add CONFIG_PREEMPT_DYNAMIC=n to NOPREEMPT scenario

It is no longer possible to build a kernel with a preemption-disabled
RCU without use of CONFIG_PREEMPT_DYNAMIC=n. This commit therefore
adds CONFIG_PREEMPT_DYNAMIC=n to the refscale torture type's NOPREEMPT
scenario file.

Signed-off-by: Paul E. McKenney <[email protected]>
---
tools/testing/selftests/rcutorture/configs/refscale/NOPREEMPT | 1 +
1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/rcutorture/configs/refscale/NOPREEMPT b/tools/testing/selftests/rcutorture/configs/refscale/NOPREEMPT
index ef2b501a6971..67f9d2998afd 100644
--- a/tools/testing/selftests/rcutorture/configs/refscale/NOPREEMPT
+++ b/tools/testing/selftests/rcutorture/configs/refscale/NOPREEMPT
@@ -2,6 +2,7 @@ CONFIG_SMP=y
CONFIG_PREEMPT_NONE=y
CONFIG_PREEMPT_VOLUNTARY=n
CONFIG_PREEMPT=n
+CONFIG_PREEMPT_DYNAMIC=n
#CHECK#CONFIG_PREEMPT_RCU=n
CONFIG_HZ_PERIODIC=n
CONFIG_NO_HZ_IDLE=y
--
2.40.1

2023-07-17 18:25:27

by Paul E. McKenney

Subject: [PATCH rcu 3/3] 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 <[email protected]>
---
kernel/rcu/refscale.c | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 71d138573856..91a0fd0d4d9a 100644
--- 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,
};

--
2.40.1