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

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Message-ID: <f4c67729-3944-4dc4-9cd3-6e07755ddfc7@paulmck-laptop>
Date: Thu, 10 Jul 2025 17:41:20 -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 2/8] shazptr: Add refscale test

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@...il.com>

One nit below, but with or without that changed:

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