netdev - Re: [PATCH v8 06/16] tracepoint: use new hashtable implementation

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Message-ID: <20121030192028.GC9427@Krystal>
Date:	Tue, 30 Oct 2012 15:20:28 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	torvalds@...ux-foundation.org, tj@...nel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, paul.gortmaker@...driver.com,
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	ebiederm@...ssion.com, aarcange@...hat.com, ericvh@...il.com,
	netdev@...r.kernel.org, josh@...htriplett.org,
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	dm-devel@...hat.com, neilb@...e.de, ccaulfie@...hat.com,
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	dev@...nvswitch.org, rds-devel@....oracle.com, lw@...fujitsu.com
Subject: Re: [PATCH v8 06/16] tracepoint: use new hashtable implementation

* Sasha Levin (levinsasha928@...il.com) wrote:
> Switch tracepoints to use the new hashtable implementation. This reduces the
> amount of generic unrelated code in the tracepoints.
> 
> Signed-off-by: Sasha Levin <levinsasha928@...il.com>

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

> ---
>  kernel/tracepoint.c | 25 +++++++++----------------
>  1 file changed, 9 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index d96ba22..5b599f1 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -26,6 +26,7 @@
>  #include <linux/slab.h>
>  #include <linux/sched.h>
>  #include <linux/static_key.h>
> +#include <linux/hashtable.h>
>  
>  extern struct tracepoint * const __start___tracepoints_ptrs[];
>  extern struct tracepoint * const __stop___tracepoints_ptrs[];
> @@ -49,8 +50,7 @@ static LIST_HEAD(tracepoint_module_list);
>   * Protected by tracepoints_mutex.
>   */
>  #define TRACEPOINT_HASH_BITS 6
> -#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
> -static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
> +static DEFINE_HASHTABLE(tracepoint_table, TRACEPOINT_HASH_BITS);
>  
>  /*
>   * Note about RCU :
> @@ -191,16 +191,15 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
>   */
>  static struct tracepoint_entry *get_tracepoint(const char *name)
>  {
> -	struct hlist_head *head;
>  	struct hlist_node *node;
>  	struct tracepoint_entry *e;
>  	u32 hash = jhash(name, strlen(name), 0);
>  
> -	head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
> -	hlist_for_each_entry(e, node, head, hlist) {
> +	hash_for_each_possible(tracepoint_table, e, node, hlist, hash) {
>  		if (!strcmp(name, e->name))
>  			return e;
>  	}
> +
>  	return NULL;
>  }
>  
> @@ -210,19 +209,13 @@ static struct tracepoint_entry *get_tracepoint(const char *name)
>   */
>  static struct tracepoint_entry *add_tracepoint(const char *name)
>  {
> -	struct hlist_head *head;
> -	struct hlist_node *node;
>  	struct tracepoint_entry *e;
>  	size_t name_len = strlen(name) + 1;
>  	u32 hash = jhash(name, name_len-1, 0);
>  
> -	head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
> -	hlist_for_each_entry(e, node, head, hlist) {
> -		if (!strcmp(name, e->name)) {
> -			printk(KERN_NOTICE
> -				"tracepoint %s busy\n", name);
> -			return ERR_PTR(-EEXIST);	/* Already there */
> -		}
> +	if (get_tracepoint(name)) {
> +		printk(KERN_NOTICE "tracepoint %s busy\n", name);
> +		return ERR_PTR(-EEXIST);	/* Already there */
>  	}
>  	/*
>  	 * Using kmalloc here to allocate a variable length element. Could
> @@ -234,7 +227,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
>  	memcpy(&e->name[0], name, name_len);
>  	e->funcs = NULL;
>  	e->refcount = 0;
> -	hlist_add_head(&e->hlist, head);
> +	hash_add(tracepoint_table, &e->hlist, hash);
>  	return e;
>  }
>  
> @@ -244,7 +237,7 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
>   */
>  static inline void remove_tracepoint(struct tracepoint_entry *e)
>  {
> -	hlist_del(&e->hlist);
> +	hash_del(&e->hlist);
>  	kfree(e);
>  }
>  
> -- 
> 1.7.12.4
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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