linux-kernel - Re: [PATCH 1/2] rcuperf: Add support to vary the slab object sizes

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Message-ID: <20200118120049.GA10134@pc636>
Date:   Sat, 18 Jan 2020 13:00:49 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, urezki@...il.com,
        Davidlohr Bueso <dave@...olabs.net>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Paul E. McKenney" <paulmck@...nel.org>, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 1/2] rcuperf: Add support to vary the slab object sizes

Hello, Joel.

> This patch varies the allocated size of objects to be more realistic in
> comparison to production workloads.
> 
> Cc: urezki@...il.com
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> 
> ---
>  kernel/rcu/rcuperf.c | 48 +++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 41 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
> index da94b89cd531..1fd0cc72022e 100644
> --- a/kernel/rcu/rcuperf.c
> +++ b/kernel/rcu/rcuperf.c
> @@ -87,6 +87,7 @@ torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
>  torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
>  torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
>  torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() perf test?");
> +torture_param(bool, kfree_vary_obj_size, 0, "Vary the kfree_rcu object size");
>  
>  static char *perf_type = "rcu";
>  module_param(perf_type, charp, 0444);
> @@ -599,17 +600,29 @@ static int kfree_nrealthreads;
>  static atomic_t n_kfree_perf_thread_started;
>  static atomic_t n_kfree_perf_thread_ended;
>  
> -struct kfree_obj {
> -	char kfree_obj[8];
> -	struct rcu_head rh;
> -};
> +/*
> + * Define a kfree_obj with size as the @size parameter + the size of rcu_head
> + * (rcu_head is 16 bytes on 64-bit arch).
> + */
> +#define DEFINE_KFREE_OBJ(size)	\
> +struct kfree_obj_ ## size {	\
> +	char kfree_obj[size];	\
> +	struct rcu_head rh;	\
> +}
> +
> +/* This should goto the right sized slabs on both 32-bit and 64-bit arch */
> +DEFINE_KFREE_OBJ(16); // goes on kmalloc-32 slab
> +DEFINE_KFREE_OBJ(32); // goes on kmalloc-64 slab
> +DEFINE_KFREE_OBJ(64); // goes on kmalloc-96 slab
> +DEFINE_KFREE_OBJ(96); // goes on kmalloc-128 slab
>  
>  static int
>  kfree_perf_thread(void *arg)
>  {
>  	int i, loop = 0;
>  	long me = (long)arg;
> -	struct kfree_obj *alloc_ptr;
> +	void *alloc_ptr;
> +
>  	u64 start_time, end_time;
>  
>  	VERBOSE_PERFOUT_STRING("kfree_perf_thread task started");
> @@ -627,11 +640,32 @@ kfree_perf_thread(void *arg)
>  
>  	do {
>  		for (i = 0; i < kfree_alloc_num; i++) {
> -			alloc_ptr = kmalloc(sizeof(struct kfree_obj), GFP_KERNEL);
> +			int kfree_type = i % 4;
> +
> +			// Allocate only kfree_obj_16 if rcuperf.kfree_vary_obj_size not passed.
> +			if (!kfree_vary_obj_size)
> +				kfree_type = 0;
> +
> +			if (kfree_type == 0)
> +				alloc_ptr = kmalloc(sizeof(struct kfree_obj_16), GFP_KERNEL);
> +			else if (kfree_type == 1)
> +				alloc_ptr = kmalloc(sizeof(struct kfree_obj_32), GFP_KERNEL);
> +			else if (kfree_type == 2)
> +				alloc_ptr = kmalloc(sizeof(struct kfree_obj_64), GFP_KERNEL);
> +			else
> +				alloc_ptr = kmalloc(sizeof(struct kfree_obj_96),  GFP_KERNEL);
> +
>  			if (!alloc_ptr)
>  				return -ENOMEM;
>  
> -			kfree_rcu(alloc_ptr, rh);
> +			if (kfree_type == 0)
> +				kfree_rcu((struct kfree_obj_16 *)alloc_ptr, rh);
> +			else if (kfree_type == 1)
> +				kfree_rcu((struct kfree_obj_32 *)alloc_ptr, rh);
> +			else if (kfree_type == 2)
> +				kfree_rcu((struct kfree_obj_64 *)alloc_ptr, rh);
> +			else
> +				kfree_rcu((struct kfree_obj_96 *)alloc_ptr, rh);
>  		}
>  
>  		cond_resched();
> -- 
> 2.25.0.rc1.283.g88dfdc4193-goog
> 

Good point and patch!

Tested-by: Uladzislau Rezki (Sony) <urezki@...il.com>

--
Vlad Rezki