Re: [PATCH 5/5] Add option to specify ramp period by amount of IO

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

On 12/18/25 01:17, Jan Kara wrote:
> In some cases the ramp up period is not easy to define by amount of
> time. This is for example a case of buffered writes measurement where we
> want to start measuring only once dirty throttling kicks in. The time
> until dirty throttling kicks in depends on dirty limit (easy to figure
> out) and speed of writes to the page cache (difficult to know in
> advance). Add option ramp_size which determines the ramp up period by
> the amount of IO written (either by each job or by each group when group
> reporting is enabled).
> 
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  HOWTO.rst        |  7 +++++++
>  fio.1            |  6 ++++++
>  options.c        | 11 +++++++++++
>  thread_options.h |  2 ++
>  time.c           | 50 ++++++++++++++++++++++++++++++++++++++++++++++--
>  5 files changed, 74 insertions(+), 2 deletions(-)
> 
> diff --git a/HOWTO.rst b/HOWTO.rst
> index 9f55a73bde05..49ebae6275a6 100644
> --- a/HOWTO.rst
> +++ b/HOWTO.rst
> @@ -715,6 +715,13 @@ Time related parameters
>  	:option:`runtime` is specified.  When the unit is omitted, the value is
>  	given in seconds.
>  
> +.. option:: ramp_size=size
> +
> +	If set, fio will wait until the workload does given amount of IO before
> +	logging any performance numbers. Similar considerations apply as for
> +	``ramp_time`` option. When the unit is omitted, the value is given in
> +	megabytes.

Hmm... It may be less confusing/easier to use the regular fio "int" parameter
type here, which takes all the kilo, mega etc suffixes. This means that the
default without any suffix would be bytes, not megabytes.

Other than this, this looks good to me, and indeed super useful when testing
file systems with buffered I/Os so that the initial super fast buffering spike
is easily not accounted for.


-- 
Damien Le Moal
Western Digital Research