Re: [PATCH 1/1] backend: number of ios not as expected for trimwrite

From: Vincent Fu <vincentfu@gmail.com>
To: Ankit Kumar <ankit.kumar@samsung.com>, axboe@kernel.dk
Cc: fio@vger.kernel.org
Subject: Re: [PATCH 1/1] backend: number of ios not as expected for trimwrite
Date: Tue, 13 Sep 2022 12:07:55 -0400	[thread overview]
Message-ID: <8b947201-1c71-d151-4748-0e80cfda4d04@gmail.com> (raw)
In-Reply-To: <20220913104527.18734-2-ankit.kumar@samsung.com>

On 9/13/22 06:45, Ankit Kumar wrote:
> number_ios should be twice for trimwrite, just like size or
> io_size. Update the documentation for "rw=trimwrite" to explain the
> changes.
> 
> Signed-off-by: Ankit Kumar <ankit.kumar@samsung.com>
> ---
>   HOWTO.rst | 6 +++++-
>   backend.c | 6 ++++--
>   fio.1     | 5 ++++-
>   3 files changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/HOWTO.rst b/HOWTO.rst
> index 2c6c6dbe..924f5ed9 100644
> --- a/HOWTO.rst
> +++ b/HOWTO.rst
> @@ -1129,7 +1129,11 @@ I/O type
>   				Random mixed reads and writes.
>   		**trimwrite**
>   				Sequential trim+write sequences. Blocks will be trimmed first,
> -				then the same blocks will be written to.
> +				then the same blocks will be written to. So if ``io_size=64K``
> +				is specified, Fio will trim a total of 64K bytes and also
> +				write 64K bytes on the same trimmed blocks. This behaviour
> +				will be consistent with ``number_ios`` or other Fio options
> +				limiting the total bytes or number of I/O's.
>   
>   	Fio defaults to read if the option is not specified.  For the mixed I/O
>   	types, the default is to split them 50/50.  For certain types of I/O the
> diff --git a/backend.c b/backend.c
> index fe614f6e..ec535bcc 100644
> --- a/backend.c
> +++ b/backend.c
> @@ -971,9 +971,11 @@ static void do_io(struct thread_data *td, uint64_t *bytes_done)
>   		total_bytes += td->o.size;
>   
>   	/* In trimwrite mode, each byte is trimmed and then written, so
> -	 * allow total_bytes to be twice as big */
> -	if (td_trimwrite(td))
> +	 * allow total_bytes or number of ios to be twice as big */
> +	if (td_trimwrite(td)) {
>   		total_bytes += td->total_io_size;
> +		td->o.number_ios *= 2;
> +	}
>   
>   	while ((td->o.read_iolog_file && !flist_empty(&td->io_log_list)) ||
>   		(!flist_empty(&td->trim_list)) || !io_issue_bytes_exceeded(td) ||
> diff --git a/fio.1 b/fio.1
> index 67d7c710..c67bd464 100644
> --- a/fio.1
> +++ b/fio.1
> @@ -900,7 +900,10 @@ Random mixed reads and writes.
>   .TP
>   .B trimwrite
>   Sequential trim+write sequences. Blocks will be trimmed first,
> -then the same blocks will be written to.
> +then the same blocks will be written to. So if `io_size=64K' is specified,
> +Fio will trim a total of 64K bytes and also write 64K bytes on the same
> +trimmed blocks. This behaviour will be consistent with `number_ios' or
> +other Fio options limiting the total bytes or number of I/O's.
>   .RE
>   .P
>   Fio defaults to read if the option is not specified. For the mixed I/O

This is the right behavior because io_size and number_ios should be 
consistent. But this will require folks who have worked around the 
inconsistent behavior to adjust. I'll let Jens make the final call on 
this one.

Reviewed-by: Vincent Fu <vincent.fu@samsung.com>