linux-kernel - Re: [PATCH v11 3/3] scsi: set max_bio

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Message-ID: <DM6PR04MB7081BDEC7ECFB63D3E6345D0E73D9@DM6PR04MB7081.namprd04.prod.outlook.com>
Date:   Wed, 2 Jun 2021 12:53:11 +0000
From:   Damien Le Moal <Damien.LeMoal@....com>
To:     Changheun Lee <nanich.lee@...sung.com>,
        "hch@...radead.org" <hch@...radead.org>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
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Subject: Re: [PATCH v11 3/3] scsi: set max_bio_bytes with queue max sectors

On 2021/06/02 21:29, Changheun Lee wrote:
> Set max_bio_bytes same with queue max sectors. It will lead to fast bio
> submit when bio size is over than queue max sectors. And it might be helpful
> to align submit bio size in some case.
> 
> Signed-off-by: Changheun Lee <nanich.lee@...sung.com>
> ---
>  drivers/scsi/scsi_lib.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 532304d42f00..f6269268b0e0 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1837,6 +1837,8 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
>  	blk_queue_virt_boundary(q, shost->virt_boundary_mask);
>  	dma_set_max_seg_size(dev, queue_max_segment_size(q));
>  
> +	blk_queue_max_bio_bytes(q, queue_max_sectors(q));

Doing this unconditionally for all scsi block devices is probably not a good
idea. Cannot this be moved to the LLD handling the devices that actually need it ?

> +
>  	/*
>  	 * Set a reasonable default alignment:  The larger of 32-byte (dword),
>  	 * which is a common minimum for HBAs, and the minimum DMA alignment,
> 


-- 
Damien Le Moal
Western Digital Research