Re: [PATCH] scsi: default to scsi-mq

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Fri, 2017-06-16 at 10:27 +0200, Christoph Hellwig wrote:
> Remove the SCSI_MQ_DEFAULT config option and default to the blk-mq I/O
> path now that we had plenty of testing, and have I/O schedulers for
> blk-mq.  The module option to disable the blk-mq path is kept around
> for now.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/scsi/Kconfig | 11 -----------
>  drivers/scsi/scsi.c  |  4 ----
>  2 files changed, 15 deletions(-)
> 
> diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
> index 3c52867dfe28..d384f4f86c26 100644
> --- a/drivers/scsi/Kconfig
> +++ b/drivers/scsi/Kconfig
> @@ -47,17 +47,6 @@ config SCSI_NETLINK
>  	default	n
>  	depends on NET
>  
> -config SCSI_MQ_DEFAULT
> -	bool "SCSI: use blk-mq I/O path by default"
> -	depends on SCSI
> -	---help---
> -	  This option enables the new blk-mq based I/O path for SCSI
> -	  devices by default.  With the option the scsi_mod.use_blk_mq
> -	  module/boot option defaults to Y, without it to N, but it can
> -	  still be overridden either way.
> -
> -	  If unsure say N.
> -
>  config SCSI_PROC_FS
>  	bool "legacy /proc/scsi/ support"
>  	depends on SCSI && PROC_FS
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 1bf274e3b2b6..3d38c6d463b8 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -800,11 +800,7 @@ MODULE_LICENSE("GPL");
>  module_param(scsi_logging_level, int, S_IRUGO|S_IWUSR);
>  MODULE_PARM_DESC(scsi_logging_level, "a bit mask of logging levels");
>  
> -#ifdef CONFIG_SCSI_MQ_DEFAULT
>  bool scsi_use_blk_mq = true;
> -#else
> -bool scsi_use_blk_mq = false;
> -#endif
>  module_param_named(use_blk_mq, scsi_use_blk_mq, bool, S_IWUSR | S_IRUGO);
>  
>  static int __init init_scsi(void)

Since a fix for the performance regression triggered by this patch will be upstream
soon (see also https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-linus&id=32825c45ff8f4cce937ab85b030dc693ceb1aa0a):

Acked-by: Bart Van Assche <bart.vanassche@wdc.com>