linux-kernel - Re: [RFC PATCH 3/8] shazptr: Add refscale test for wildcard

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Message-ID: <ccb7d433-0ff8-4bbc-8c76-be2d391fb06a@paulmck-laptop>
Date: Thu, 10 Jul 2025 17:42:40 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Boqun Feng <boqun.feng@...il.com>
Cc: Breno Leitao <leitao@...ian.org>, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>, aeh@...a.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	edumazet@...gle.com, jhs@...atatu.com, kernel-team@...a.com,
	Erik Lundgren <elundgren@...a.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Uladzislau Rezki <urezki@...il.com>, rcu@...r.kernel.org
Subject: Re: [RFC PATCH 3/8] shazptr: Add refscale test for wildcard

On Sun, Apr 13, 2025 at 11:00:50PM -0700, Boqun Feng wrote:
> 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@...il.com>

With or without the same ref_shazptr_init() fix as the preview patch:

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

> ---
>  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
>