linux-kernel - Re: [PATCH v3 1/1] rcuscale: add kfree

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Date:   Wed, 17 Feb 2021 13:24:04 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Axtens <dja@...ens.net>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH v3 1/1] rcuscale: add kfree_rcu() single-argument scale
 test

On Wed, Feb 17, 2021 at 07:51:10PM +0100, Uladzislau Rezki (Sony) wrote:
> To stress and test a single argument of kfree_rcu() call, we
> should to have a special coverage for it. We used to have it
> in the test-suite related to vmalloc stressing. The reason is
> the rcuscale is a correct place for RCU related things.
> 
> Therefore introduce two torture_param() variables, one is for
> single-argument scale test and another one for double-argument
> scale test.
> 
> By default kfree_rcu_test_single and kfree_rcu_test_double are
> initialized to false. If both have the same value (false or true)
> both are randomly tested, otherwise only the one with value true
> is tested. The value of this is that it allows testing of both
> options with one test.
> 
> Suggested-by: Paul E. McKenney <paulmck@...nel.org>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>

Queued with the usual wordsmithing, thank you!

							Thanx, Paul

> ---
>  kernel/rcu/rcuscale.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> index 06491d5530db..0fb540e2b22b 100644
> --- a/kernel/rcu/rcuscale.c
> +++ b/kernel/rcu/rcuscale.c
> @@ -625,6 +625,8 @@ rcu_scale_shutdown(void *arg)
>  torture_param(int, kfree_nthreads, -1, "Number of threads running loops of kfree_rcu().");
>  torture_param(int, kfree_alloc_num, 8000, "Number of allocations and frees done in an iteration.");
>  torture_param(int, kfree_loops, 10, "Number of loops doing kfree_alloc_num allocations and frees.");
> +torture_param(bool, kfree_rcu_test_single, false, "Do we run a kfree_rcu() single-argument scale test?");
> +torture_param(bool, kfree_rcu_test_double, false, "Do we run a kfree_rcu() double-argument scale test?");
>  
>  static struct task_struct **kfree_reader_tasks;
>  static int kfree_nrealthreads;
> @@ -644,10 +646,13 @@ kfree_scale_thread(void *arg)
>  	struct kfree_obj *alloc_ptr;
>  	u64 start_time, end_time;
>  	long long mem_begin, mem_during = 0;
> +	bool kfree_rcu_test_both;
> +	DEFINE_TORTURE_RANDOM(tr);
>  
>  	VERBOSE_SCALEOUT_STRING("kfree_scale_thread task started");
>  	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
>  	set_user_nice(current, MAX_NICE);
> +	kfree_rcu_test_both = (kfree_rcu_test_single == kfree_rcu_test_double);
>  
>  	start_time = ktime_get_mono_fast_ns();
>  
> @@ -670,7 +675,15 @@ kfree_scale_thread(void *arg)
>  			if (!alloc_ptr)
>  				return -ENOMEM;
>  
> -			kfree_rcu(alloc_ptr, rh);
> +			// By default kfree_rcu_test_single and kfree_rcu_test_double are
> +			// initialized to false. If both have the same value (false or true)
> +			// both are randomly tested, otherwise only the one with value true
> +			// is tested.
> +			if ((kfree_rcu_test_single && !kfree_rcu_test_double) ||
> +					(kfree_rcu_test_both && torture_random(&tr) & 0x800))
> +				kfree_rcu(alloc_ptr);
> +			else
> +				kfree_rcu(alloc_ptr, rh);
>  		}
>  
>  		cond_resched();
> -- 
> 2.20.1
>