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Re: [dm-devel] [PATCH 3/7] dm: add reserved_bio_based_ios module parameter



We don't need this. bio-based i/o should be fine with a small mempool, 
there is no need to make it tunable.

Mikulas


On Thu, 12 Sep 2013, Mike Snitzer wrote:

> Allow user to change the number of IOs that are reserved by
> bio-based DM's mempools by writing to this file:
> /sys/module/dm_mod/parameters/reserved_bio_based_ios
> 
> The default value is RESERVED_BIO_BASED_IOS (16).
> 
> Signed-off-by: Mike Snitzer <snitzer redhat com>
> ---
>  drivers/md/dm.c | 42 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 8553d03..b44ae19 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -217,6 +217,17 @@ static struct kmem_cache *_io_cache;
>  static struct kmem_cache *_rq_tio_cache;
>  
>  /*
> + * Bio-based DM's mempools' reserved IOs set by the user
> + */
> +static unsigned reserved_bio_based_ios;
> +
> +/*
> + * A copy of reserved_bio_based_ios because it can change anytime.
> + * If values disagree, the user has changed reserved_bio_based_ios.
> + */
> +static unsigned reserved_bio_based_ios_latch;
> +
> +/*
>   * Request-based DM's mempools' reserved IOs set by the user
>   */
>  static unsigned reserved_rq_based_ios;
> @@ -228,10 +239,26 @@ static unsigned reserved_rq_based_ios;
>  static unsigned reserved_rq_based_ios_latch;
>  
>  /*
> - * This mutex protects reserved_rq_based_ios_latch.
> + * This mutex protects reserved_bio_based_ios_latch and reserved_rq_based_ios_latch.
>   */
>  static DEFINE_MUTEX(dm_mempools_lock);
>  
> +static void __reserved_bio_based_ios_refresh(void)
> +{
> +	BUG_ON(!mutex_is_locked(&dm_mempools_lock));
> +
> +	reserved_bio_based_ios_latch = ACCESS_ONCE(reserved_bio_based_ios);
> +
> +	/*
> +	 * If the user uses "0", it means default.  Modify
> +	 * reserved_bio_based_ios to report the default to the user.
> +	 */
> +	if (!reserved_bio_based_ios_latch) {
> +		(void)cmpxchg(&reserved_bio_based_ios, 0, RESERVED_BIO_BASED_IOS);
> +		reserved_bio_based_ios_latch = reserved_bio_based_ios;
> +	}
> +}
> +
>  static void __reserved_request_based_ios_refresh(void)
>  {
>  	BUG_ON(!mutex_is_locked(&dm_mempools_lock));
> @@ -274,6 +301,7 @@ static int __init local_init(void)
>  		_major = r;
>  
>  	mutex_lock(&dm_mempools_lock);
> +	__reserved_bio_based_ios_refresh();
>  	__reserved_request_based_ios_refresh();
>  	mutex_unlock(&dm_mempools_lock);
>  
> @@ -2899,7 +2927,14 @@ struct dm_md_mempools *dm_alloc_md_mempools(unsigned type, unsigned integrity, u
>  
>  	if (type == DM_TYPE_BIO_BASED) {
>  		cachep = _io_cache;
> -		pool_size = RESERVED_BIO_BASED_IOS;
> +
> +		mutex_lock(&dm_mempools_lock);
> +		/* Check if reserved_bio_based_ios changed. */
> +		if (reserved_bio_based_ios != reserved_bio_based_ios_latch)
> +			__reserved_bio_based_ios_refresh();
> +		pool_size = reserved_bio_based_ios_latch;
> +		mutex_unlock(&dm_mempools_lock);
> +
>  		front_pad = roundup(per_bio_data_size, __alignof__(struct dm_target_io)) + offsetof(struct dm_target_io, clone);
>  	} else if (type == DM_TYPE_REQUEST_BASED) {
>  		cachep = _rq_tio_cache;
> @@ -2969,6 +3004,9 @@ module_exit(dm_exit);
>  module_param(major, uint, 0);
>  MODULE_PARM_DESC(major, "The major number of the device mapper");
>  
> +module_param(reserved_bio_based_ios, uint, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(reserved_bio_based_ios, "Reserved IOs in bio-based mempools");
> +
>  module_param(reserved_rq_based_ios, uint, S_IRUGO | S_IWUSR);
>  MODULE_PARM_DESC(reserved_rq_based_ios, "Reserved IOs in request-based mempools");
>  
> -- 
> 1.8.1.4
> 


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