Re: [PATCH v2 4/8] doc: explain the option write_zone_remainder

[Damien Le Moal <dlemoal@kernel.org>]

On 2/16/26 16:59, Shin'ichiro Kawasaki wrote:
> The recent commit introduced the option write_zone_remainder. Explain
> how it changes handling of zone end remainders. Also, amend the zbd
> zone mode description to explain the default handling of zone end
> remainders.
> 
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> ---
>  HOWTO.rst | 26 +++++++++++++++++++++++++-
>  fio.1     | 25 ++++++++++++++++++++++---
>  2 files changed, 47 insertions(+), 4 deletions(-)
> 
> diff --git a/HOWTO.rst b/HOWTO.rst
> index d31851e9..148c650e 100644
> --- a/HOWTO.rst
> +++ b/HOWTO.rst
> @@ -1034,7 +1034,14 @@ Target file/device
>  				all zones instead of being restricted to a
>  				single zone. The :option:`zoneskip` parameter
>  				is ignored. :option:`zonerange` and
> -				:option:`zonesize` must be identical.
> +				:option:`zonesize` must be identical. When the
> +				specified block size is not aligned with the
> +				zone size or the write pointer positions at
> +				workload start, write workloads create unwritten

				If the size of the unwritten space in a zone is
				not a multiple of the specified block size at
				workload start, write workloads create unwritten

> +				remainder areas at the ends of zones and keep
> +				the zones in open conditions. To free up the
> +				open zone resources, fio issues zone finish
> +				operations to the zones with the remainders.
>  				Trim is handled using a zone reset operation.
>  				Trim only considers non-empty sequential write
>  				required and sequential write preferred zones.
> @@ -1167,6 +1174,23 @@ Target file/device
>  	asynchronous IO engine and :option:`verify` workload are specified,
>  	errors out. Default: false.
>  
> +.. option:: write_zone_remainders=bool
> +
> +	When the specified block size is not aligned with the zone size or the
> +	write pointer positions at workload start, write workloads create

Same as above.

> +	unwritten remainder areas at the ends of zones. By default, fio issues
> +	zone finish operations on such zones, transitioning them to the full
> +	condition and freeing up open zone resources. However, zone finish
> +	operations introduces waits for in-flight writes, reducing overall write
> +	throughput. If this option is specified, fio writes data to the
> +	remainder areas instead of performing zone finish operations. This
> +	improves write throughput by avoiding waits for in-flight writes,
> +	particularly in asynchronous write workloads. The drawback of this
> +	option is that it requires fio to perform writes smaller than the
> +	minimum block size. Consequently, the option :option:`norandommap` must
> +	be set. If :option:`norandommap` is not set, it is automatically set.
> +	Default: false.

With the above and similar fix in the man page, feel free to add:

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research