Re: [PATCH 1/5] common/scsi_debug: don't slow down I/O

[John Garry <john.g.garry@oracle.com>]

On 21/08/2026 06:11, Christoph Hellwig wrote:
> scsi_debug by defaults delays I/O 

Maybe we can just make delay=0 default for that driver. Or use ndelay > 0.

> and doesn't support multi-page I/O.
> Flipping these defaults speed up each test using scsi_debug by more than
> an order of magnitute on my test systems.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

FWIW:

Reviewed-by: John Garry <john.g.garry@oracle.com>

> ---
>   common/scsi_debug | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/common/scsi_debug b/common/scsi_debug
> index c3fe7be623fa..af51905dc4ba 100644
> --- a/common/scsi_debug
> +++ b/common/scsi_debug
> @@ -59,9 +59,19 @@ _get_scsi_debug_dev()
>   		let physical=physical/2
>   		let phys_exp=phys_exp+1
>   	done
> -	opts="sector_size=$logical physblk_exp=$phys_exp lowest_aligned=$unaligned dev_size_mb=$size $@"
> -	echo "scsi_debug options $opts" >> $seqres.full
> -	modprobe scsi_debug $opts
> +
> +	local opts=(
> +		"sector_size=$logical"
> +		"physblk_exp=$phys_exp"
> +		"lowest_aligned=$unaligned"
> +		"dev_size_mb=$size"
> +		"delay=0"
> +		"clustering=1"
> +	)
> +	opts+=("$@")
> +
> +	echo "scsi_debug options ${opts[*]}" >> $seqres.full
> +	modprobe scsi_debug "${opts[@]}"
>   	[ $? -eq 0 ] || _fail "scsi_debug modprobe failed"
>   	$UDEV_SETTLE_PROG
>   	device=`grep -wl scsi_debug /sys/block/sd*/device/model | awk -F / '{print $4}'`