linux-kernel - Re: [PATCH] block: remove artifical max_hw

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Date:	Mon, 22 Sep 2014 22:59:47 -0700
From:	Christoph Hellwig <hch@...radead.org>
To:	Christoph Hellwig <hch@....de>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org
Subject: Re: [PATCH] block: remove artifical max_hw_sectors cap

ping?

On Sat, Sep 06, 2014 at 04:08:05PM -0700, Christoph Hellwig wrote:
> Set max_sectors to the value the drivers provides as hardware limit by
> default.  Linux had proper I/O throttling for a long time and doesn't
> rely on a artifically small maximum I/O size anymore.  By not limiting
> the I/O size by default we remove an annoying tuning step required for
> most Linux installation.
> 
> Note that both the user, and if absolutely required the driver can still
> impose a limit for FS requests below max_hw_sectors_kb.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  block/blk-settings.c       | 4 +---
>  drivers/block/aoe/aoeblk.c | 2 +-
>  include/linux/blkdev.h     | 1 -
>  3 files changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index f1a1795..f52c223 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -257,9 +257,7 @@ void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_
>  		       __func__, max_hw_sectors);
>  	}
>  
> -	limits->max_hw_sectors = max_hw_sectors;
> -	limits->max_sectors = min_t(unsigned int, max_hw_sectors,
> -				    BLK_DEF_MAX_SECTORS);
> +	limits->max_sectors = limits->max_hw_sectors = max_hw_sectors;
>  }
>  EXPORT_SYMBOL(blk_limits_max_hw_sectors);
>  
> diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
> index dd73e1f..46c282f 100644
> --- a/drivers/block/aoe/aoeblk.c
> +++ b/drivers/block/aoe/aoeblk.c
> @@ -395,7 +395,7 @@ aoeblk_gdalloc(void *vp)
>  	WARN_ON(d->flags & DEVFL_TKILL);
>  	WARN_ON(d->gd);
>  	WARN_ON(d->flags & DEVFL_UP);
> -	blk_queue_max_hw_sectors(q, BLK_DEF_MAX_SECTORS);
> +	blk_queue_max_hw_sectors(q, 1024);
>  	q->backing_dev_info.name = "aoe";
>  	q->backing_dev_info.ra_pages = READ_AHEAD / PAGE_CACHE_SIZE;
>  	d->bufpool = mp;
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 518b465..7e3c172 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1192,7 +1192,6 @@ extern int blk_verify_command(unsigned char *cmd, fmode_t has_write_perm);
>  enum blk_default_limits {
>  	BLK_MAX_SEGMENTS	= 128,
>  	BLK_SAFE_MAX_SECTORS	= 255,
> -	BLK_DEF_MAX_SECTORS	= 1024,
>  	BLK_MAX_SEGMENT_SIZE	= 65536,
>  	BLK_SEG_BOUNDARY_MASK	= 0xFFFFFFFFUL,
>  };
> -- 
> 1.9.1
> 
> --
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