Re: [B.A.T.M.A.N.] [PATCHv2 5/5] batman-adv: Allow to use different sized hash locks array

[Antonio Quartulli <ordex@autistici.org>]

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On Mon, Nov 26, 2012 at 12:58:32PM +0100, Sven Eckelmann wrote:
> The amount of locks of a hash directly affects the parallelity when all access
> independent parts of the hash. But this also affects the amount of memory used
> for each hash. Allowing to decouple the hash size and the lock size allows to
> reduce this memory consumption for hashes which don't allow this parallelism.
> 
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
>  bridge_loop_avoidance.c |   28 ++++++++++++++--------------
>  distributed-arp-table.c |   16 ++++++++--------
>  distributed-arp-table.h |    6 +++---
>  hash.h                  |   19 +++++++++----------
>  originator.c            |    6 ++++--
>  originator.h            |   13 +++++--------
>  translation-table.c     |   22 ++++++++++++++--------
>  vis.c                   |    8 ++++----
>  8 files changed, 61 insertions(+), 57 deletions(-)
> 
> diff --git a/bridge_loop_avoidance.c b/bridge_loop_avoidance.c
> index 1a78bac..781119f 100644
> --- a/bridge_loop_avoidance.c
> +++ b/bridge_loop_avoidance.c
> @@ -38,7 +38,7 @@ static void batadv_bla_send_announce(struct batadv_priv *bat_priv,
>  				     struct batadv_backbone_gw *backbone_gw);
>  
>  /* return the index of the claim */
> -static inline uint32_t batadv_choose_claim(const void *data, uint32_t size)
> +static inline uint32_t batadv_choose_claim(const void *data)
>  {
>  	struct batadv_claim *claim = (struct batadv_claim *)data;
>  	uint32_t hash;
> @@ -46,12 +46,11 @@ static inline uint32_t batadv_choose_claim(const void *data, uint32_t size)
>  	hash = jhash(&claim->addr, sizeof(claim->addr), 0);
>  	hash = jhash(&claim->vid, sizeof(claim->vid), hash);
>  
> -	return hash % size;
> +	return hash;

I do not fully understand how having the mod operation inside the function would
prevent the decoupling. Why you need to move it out?

Cheers,

-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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