[PATCH v4 12/13] null_blk: use zone_size_sects_shift for power of 2 zoned devices

Pankaj Raghav
2022-05-16T16:55:11Z

Instead of doing is_power_of_2 and ilog2 operation for every IO, cache
the zone_size_sects_shift variable and use it for power of 2 zoned
devices.

This variable will be set to zero for non power of 2 zoned devices.

Suggested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
drivers/block/null_blk/null_blk.h | 6 ++++++
drivers/block/null_blk/zoned.c | 10 ++++++++--
2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h
index 4525a65e1..3bbae8be4 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -76,6 +76,12 @@ struct nullb_device {
unsigned int imp_close_zone_no;
struct nullb_zone *zones;
sector_t zone_size_sects;
+ /*
+ * zone_size_sects_shift is only useful when the zone size is
+ * power of 2. This variable is set to zero when zone size is non
+ * power of 2.
+ */
+ unsigned int zone_size_sects_shift;
bool need_zone_res_mgmt;
spinlock_t zone_res_lock;

diff --git a/drivers/block/null_blk/zoned.c b/drivers/block/null_blk/zoned.c
index 00c34e65e..806bef98a 100644
--- a/drivers/block/null_blk/zoned.c
+++ b/drivers/block/null_blk/zoned.c
@@ -13,8 +13,8 @@ static inline sector_t mb_to_sects(unsigned long mb)

static inline unsigned int null_zone_no(struct nullb_device *dev, sector_t sect)
{
- if (is_power_of_2(dev->zone_size_sects))
- return sect >> ilog2(dev->zone_size_sects);
+ if (dev->zone_size_sects_shift)
+ return sect >> dev->zone_size_sects_shift;

return div64_u64(sect, dev->zone_size_sects);
}
@@ -82,6 +82,12 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
zone_capacity_sects = mb_to_sects(dev->zone_capacity);
dev_capacity_sects = mb_to_sects(dev->size);
dev->zone_size_sects = mb_to_sects(dev->zone_size);
+
+ if (is_power_of_2(dev->zone_size_sects))
+ dev->zone_size_sects_shift = ilog2(dev->zone_size_sects);
+ else
+ dev->zone_size_sects_shift = 0;
+
dev->nr_zones =
div64_u64(roundup(dev_capacity_sects, dev->zone_size_sects),
dev->zone_size_sects);
--
2.25.1