Re: [RFC PATCH 2/8] shazptr: Add refscale test

Paul E. McKenney
2025-07-11T00:41:20Z

On Sun, Apr 13, 2025 at 11:00:49PM -0700, Boqun Feng wrote:
> Add the refscale test for shazptr to measure the reader side
> performance.
>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

One nit below, but with or without that changed:

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

> ---
> kernel/rcu/refscale.c | 39 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 39 insertions(+)
>
> diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
> index f11a7c2af778..154520e4ee4c 100644
> --- a/kernel/rcu/refscale.c
> +++ b/kernel/rcu/refscale.c
> @@ -29,6 +29,7 @@
> #include <linux/reboot.h>
> #include <linux/sched.h>
> #include <linux/seq_buf.h>
> +#include <linux/shazptr.h>
> #include <linux/spinlock.h>
> #include <linux/smp.h>
> #include <linux/stat.h>
> @@ -890,6 +891,43 @@ static const struct ref_scale_ops typesafe_seqlock_ops = {
> .name = "typesafe_seqlock"
> };
>
> +static void ref_shazptr_read_section(const int nloops)
> +{
> + int i;
> +
> + for (i = nloops; i >= 0; i--) {
> + preempt_disable();
> + { guard(shazptr)(ref_shazptr_read_section); }
> + preempt_enable();
> + }
> +}
> +
> +static void ref_shazptr_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);
> + un_delay(udl, ndl);
> + }
> + preempt_enable();
> + }
> +}
> +
> +static bool ref_shazptr_init(void)
> +{
> + return true;
> +}
> +
> +static const struct ref_scale_ops shazptr_ops = {
> + .init = ref_shazptr_init,

You could make this NULL and drop the ref_shazptr_init() function.
As in drop the above .init= initialization along with that function.

Of course, the same is true of the existing rcu_sync_scale_init()
function, so I cannot fault you here. ;-)

> + .readsection = ref_shazptr_read_section,
> + .delaysection = ref_shazptr_delay_section,
> + .name = "shazptr"
> +};
> +
> static void rcu_scale_one_reader(void)
> {
> if (readdelay <= 0)
> @@ -1197,6 +1235,7 @@ 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,
> };
>
> if (!torture_init_begin(scale_type, verbose))
> --
> 2.47.1
>