Re: [PATCH] lookup_object: prioritize recently found objects

From: Johannes Sixt <j.sixt@viscovery.net>
Date: May 2, 2013, 06:44 UTC
Message-ID: <51820B37.8010503@viscovery.net>
In-Reply-To: <20130501203449.GA12535@sigill.intra.peff.net>

Am 5/1/2013 22:34, schrieb Jeff King:

Show 25 quoted lines

>  struct object *lookup_object(const unsigned char *sha1)
>  {
> -	unsigned int i;
> +	unsigned int i, first;
>  	struct object *obj;
>  
>  	if (!obj_hash)
>  		return NULL;
>  
> -	i = hashtable_index(sha1);
> +	first = i = hashtable_index(sha1);
>  	while ((obj = obj_hash[i]) != NULL) {
>  		if (!hashcmp(sha1, obj->sha1))
>  			break;
> @@ -85,6 +85,11 @@ struct object *lookup_object(const unsigned char *sha1)
>  		if (i == obj_hash_size)
>  			i = 0;
>  	}
> +	if (obj && i != first) {
> +		struct object *tmp = obj_hash[i];
> +		obj_hash[i] = obj_hash[first];
> +		obj_hash[first] = tmp;
> +	}
>  	return obj;
>  }

This is one of the places where I think the code does not speak for itself and a comment is warranted: The new if statement is not about correctness, but about optimization:

		/*
		 * Move object to where we started to look for it
		 * so that we do not need to walk the hash table
		 * the next time we look for it.
		 */

or something.

-- Hannes