[ltt-dev] [PATCH 7/9] rculfhash: Simplify lookup_bucket()

[Mathieu Desnoyers]

* Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
> They are the same, but I don't think the compiler
> can optimize it.

Can you double-check this by comparing assembly output ?

> 
> And it also helps for understanding the following code.

I try to use "get_count_order" in the algorithms everywhere so we have
only a single semantic to keep in mind.

Thanks,

Mathieu

> 
> Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
> ---
>  rculfhash.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/rculfhash.c b/rculfhash.c
> index edbd24a..7b880d7 100644
> --- a/rculfhash.c
> +++ b/rculfhash.c
> @@ -719,7 +719,7 @@ struct _cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
>  
>  	assert(size > 0);
>  	index = hash & (size - 1);
> -	order = get_count_order_ulong(index + 1);
> +	order = fls_ulong(index);
>  
>  	dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
>  		   hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1)));
> -- 
> 1.7.4.4
> 

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