Simple helper to use when DM core code needs to appropriately size, based on num_online_cpus(), its data structures that split locks. dm_num_sharded_locks() rounds up num_online_cpus() to next power of 2 but caps return at DM_MAX_SHARDED_LOCKS (64). This heuristic may evolve as warranted, but as-is it will serve as a more informed basis for sizing the sharded lock structs in dm-bufio's dm_buffer_cache (buffer_trees) and dm-bio-prison-v1's dm_bio_prison (prison_regions). Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> --- drivers/md/dm.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/md/dm.h b/drivers/md/dm.h index 22eaed188907..18450282d0d9 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -20,6 +20,7 @@ #include <linux/completion.h> #include <linux/kobject.h> #include <linux/refcount.h> +#include <linux/log2.h> #include "dm-stats.h" @@ -228,4 +229,13 @@ void dm_free_md_mempools(struct dm_md_mempools *pools); */ unsigned int dm_get_reserved_bio_based_ios(void); +#define DM_MAX_SHARDED_LOCKS 64 + +static inline unsigned int dm_num_sharded_locks(void) +{ + unsigned int num_locks = roundup_pow_of_two(num_online_cpus()); + + return min_t(unsigned int, num_locks, DM_MAX_SHARDED_LOCKS); +} + #endif -- 2.40.0