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@xxxxxxxxxx>
> ---
> 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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