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Date: Sun, 13 Sep 2026 20:23:35 +0800
From: Zorro Lang <zlang@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: fstests@vger.kernel.org, 
	"Martin K. Petersen" <martin.petersen@oracle.com>, Kanchan Joshi <joshi.k@samsung.com>, 
	Anuj Gupta <anuj20.g@samsung.com>, John Garry <john.g.garry@oracle.com>, 
	"Darrick J. Wong" <djwong@kernel.org>, linux-scsi@vger.kernel.org
Subject: Re: [PATCH 1/6] common/scsi_debug: don't slow down I/O
Message-ID: <aqaVf-R3D9KhxCYG@zlang-mailbox>
Mail-Followup-To: Christoph Hellwig <hch@lst.de>, fstests@vger.kernel.org, 
	"Martin K. Petersen" <martin.petersen@oracle.com>, Kanchan Joshi <joshi.k@samsung.com>, 
	Anuj Gupta <anuj20.g@samsung.com>, John Garry <john.g.garry@oracle.com>, 
	"Darrick J. Wong" <djwong@kernel.org>, linux-scsi@vger.kernel.org
References: <20260911070831.1760646-1-hch@lst.de>
 <20260911070831.1760646-2-hch@lst.de>
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In-Reply-To: <20260911070831.1760646-2-hch@lst.de>

On Fri, Sep 11, 2026 at 09:08:19AM +0200, Christoph Hellwig wrote:
> scsi_debug by defaults delays I/O 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>
> Reviewed-by: John Garry <john.g.garry@oracle.com>
> Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
> ---
>  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[@]}"

Thanks Christoph, this version is good to me now.

Reviewed-by: Zorro Lang <zlang@kernel.org>

>  	[ $? -eq 0 ] || _fail "scsi_debug modprobe failed"
>  	$UDEV_SETTLE_PROG
>  	device=`grep -wl scsi_debug /sys/block/sd*/device/model | awk -F / '{print $4}'`
> -- 
> 2.53.0
>