linux-kernel - Re: [PATCH 2/2] kfree_rcu() should use kfree

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Date:   Tue, 3 Apr 2018 13:58:22 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     rao.shoaib@...cle.com
Cc:     linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
        joe@...ches.com, brouer@...hat.com, linux-mm@...ck.org
Subject: Re: [PATCH 2/2] kfree_rcu() should use kfree_bulk() interface

On Tue, Apr 03, 2018 at 10:22:53AM -0700, rao.shoaib@...cle.com wrote:
> +++ b/mm/slab.h
> @@ -80,6 +80,29 @@ extern const struct kmalloc_info_struct {
>  	unsigned long size;
>  } kmalloc_info[];
>  
> +#define	RCU_MAX_ACCUMULATE_SIZE	25
> +
> +struct rcu_bulk_free_container {
> +	struct	rcu_head rbfc_rcu;
> +	int	rbfc_entries;
> +	void	*rbfc_data[RCU_MAX_ACCUMULATE_SIZE];
> +	struct	rcu_bulk_free *rbfc_rbf;
> +};
> +
> +struct rcu_bulk_free {
> +	struct	rcu_head rbf_rcu; /* used to schedule monitor process */
> +	spinlock_t	rbf_lock;
> +	struct		rcu_bulk_free_container *rbf_container;
> +	struct		rcu_bulk_free_container *rbf_cached_container;
> +	struct		rcu_head *rbf_list_head;
> +	int		rbf_list_size;
> +	int		rbf_cpu;
> +	int		rbf_empty;
> +	int		rbf_polled;
> +	bool		rbf_init;
> +	bool		rbf_monitor;
> +};

I think you might be better off with an IDR.  The IDR can always
contain one entry, so there's no need for this 'rbf_list_head' or
__rcu_bulk_schedule_list.  The IDR contains its first 64 entries in
an array (if that array can be allocated), so it's compatible with the
kfree_bulk() interface.