Re: [PATCH v7 08/16] block,elevator: use new hashtable implementation

Mathieu Desnoyers
2012-10-29T12:20:56Z

* Sasha Levin (levinsasha928@gmail.com) wrote:
[...]
> @@ -96,6 +97,8 @@ struct elevator_type
> struct list_head list;
> };
>
> +#define ELV_HASH_BITS 6
> +
> /*
> * each queue has an elevator_queue associated with it
> */
> @@ -105,7 +108,7 @@ struct elevator_queue
> void *elevator_data;
> struct kobject kobj;
> struct mutex sysfs_lock;
> - struct hlist_head *hash;
> + DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
> unsigned int registered:1;

Hrm, so this is moving "registered" out of the elevator_queue first
cache-line by turning the pointer into a 256 or 512 bytes hash table.

Maybe we should consider moving "registered" before the "hash" field ?

Thanks,

Mathieu

> };
>
> --
> 1.7.12.4
>

--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.