netdev - Re: [RFC v3 1/7] hashtable: introduce a small and naive hashtable

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Date:	Mon, 06 Aug 2012 18:19:06 -0700
From:	Joe Perches <joe@...ches.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,
	davem@...emloft.net, rostedt@...dmis.org, mingo@...e.hu,
	ebiederm@...ssion.com, aarcange@...hat.com, ericvh@...il.com,
	netdev@...r.kernel.org, josh@...htriplett.org,
	eric.dumazet@...il.com, mathieu.desnoyers@...icios.com
Subject: Re: [RFC v3 1/7] hashtable: introduce a small and naive hashtable

On Tue, 2012-08-07 at 02:45 +0200, Sasha Levin wrote:
> This hashtable implementation is using hlist buckets to provide a simple
> hashtable to prevent it from getting reimplemented all over the kernel.

> diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h

Just trivial style notes and a typo

> +/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels. */
> +#define hash_min(val, bits) ((sizeof(val)==4)?hash_32((val), (bits)):hash_long((val), (bits)))

This is a pretty long line.  It doesn't use normal kernel spacing
style and it has unnecessary parentheses.

Maybe:

#define hash_min(val, bits)						\
	(sizeof(val) == 4 ? hash_32(val, bits) : hash_long(val, bits))

> +
> +/**
> + * hash_init - initialize a hash table
> + * @hashtable: hashtable to be initialized
> + * @bits: bit count of hashing function
> + *
> + * Initializes a hash table with 2**bits buckets.
> + */
> +static inline void hash_init(struct hlist_head *hashtable, int bits)
> +{
> +	int i;
> +
> +	for (i = 0; i < HASH_SIZE(bits); i++)
> +		INIT_HLIST_HEAD(hashtable + i);
> +}

Maybe use a struct hlist_head *last_hash_entry as a loop variable

{
	struct hlist_head *eo_hash = hashtable + HASH_SIZE(bits);

	while (hashtable < eo_hash)
		INIT_HLIST_HEAD(hashtable++);
}

The compiler might generate the same code anyway...

[]

> +/**
> + * hash_for_each_possible - iterate over all possible objects for a giver key
> + * @name: hashtable to iterate
> + * @obj: the type * to use as a loop cursor for each bucke

bucket


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