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

[Peter Zijlstra]

On Tue, Jun 24, 2025 at 08:10:55PM -0700, Boqun Feng wrote:
> Add the refscale test for shazptr to measure the reader side
> performance.
> 
> Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
> ---
>  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();

		scoped_guard (preempt)
			guard(shazptr)(ref_shazptr_read_section);

> +	}
> +}
> +
> +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();

		scoped_guard (preempt) {
			guard(shazptr)(ref_shazptr_delay_section);
			un_delay(udl, ndl);
		}


> +	}
> +}
> +
> +static bool ref_shazptr_init(void)
> +{
> +	return true;
> +}
> +
> +static const struct ref_scale_ops shazptr_ops = {
> +	.init		= ref_shazptr_init,
> +	.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))
> -- 
> 2.39.5 (Apple Git-154)
>