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Re: [dm-devel] [PATCH v2 3/5] dm mpath: reduce size of multipath structure



On 05/08/2012 11:56 PM, Mike Snitzer wrote:
> Move multipath structure's 'lock' and 'queue_size' members to eliminate
> 2 4-byte holes.  Also use a bit within a single unsigned int for each
> existing flag (saves 8-bytes).  This allows future flags to be added
> without each consuming an unsigned int.
> 
> Signed-off-by: Mike Snitzer <snitzer redhat com>
> ---
>  drivers/md/dm-mpath.c |   13 +++++++------
>  1 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index 754f38f..c351607 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -61,11 +61,11 @@ struct multipath {
>  	struct list_head list;
>  	struct dm_target *ti;
>  
> -	spinlock_t lock;
> -
>  	const char *hw_handler_name;
>  	char *hw_handler_params;
>  
> +	spinlock_t lock;
> +
>  	unsigned nr_priority_groups;
>  	struct list_head priority_groups;
>  
> @@ -81,16 +81,17 @@ struct multipath {
>  	struct priority_group *next_pg;	/* Switch to this PG if set */
>  	unsigned repeat_count;		/* I/Os left before calling PS again */
>  
> -	unsigned queue_io;		/* Must we queue all I/O? */
> -	unsigned queue_if_no_path;	/* Queue I/O if last path fails? */
> -	unsigned saved_queue_if_no_path;/* Saved state during suspension */
> +	unsigned queue_io:1;		/* Must we queue all I/O? */
> +	unsigned queue_if_no_path:1;	/* Queue I/O if last path fails? */
> +	unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
> +
>  	unsigned pg_init_retries;	/* Number of times to retry pg_init */
>  	unsigned pg_init_count;		/* Number of times pg_init called */
>  	unsigned pg_init_delay_msecs;	/* Number of msecs before pg_init retry */
>  
> +	unsigned queue_size;
>  	struct work_struct process_queued_ios;
>  	struct list_head queued_ios;
> -	unsigned queue_size;
>  
>  	struct work_struct trigger_event;
>  

Acked-by: Hannes Reinecke <hare suse de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare suse de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)


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