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

Damien Le Moal
2026-02-27T05:06:03Z

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