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