Re: [PATCH 1/1] multipath-tools: Change path checker for IBM IPR devices

[Hannes Reinecke <hare@suse.de>]

On 09/24/2014 09:57 PM, wenxiong@linux.vnet.ibm.com wrote:
> We would like to change path checker to directio for IBM IPR devices.
> 
> Signed-off-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
> ---
>  libmultipath/hwtable.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: b/libmultipath/hwtable.c
> ===================================================================
> --- a/libmultipath/hwtable.c	2014-09-23 17:39:27.000000000 -0500
> +++ b/libmultipath/hwtable.c	2014-09-23 17:40:31.419667000 -0500
> @@ -630,7 +630,7 @@ static struct hwentry default_hw[] = {
>  		.pgfailback    = -FAILBACK_IMMEDIATE,
>  		.rr_weight     = RR_WEIGHT_NONE,
>  		.no_path_retry = NO_PATH_RETRY_UNDEF,
> -		.checker_name  = TUR,
> +		.checker_name  = DIRECTIO,
>  		.prio_name     = PRIO_ALUA,
>  		.prio_args     = NULL,
>  	},
> 
> -- -- dm-devel mailing list dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
Any particular reason for doing so?

Using 'directio' has the drawback that it might stall under higher
load, as it's being added to the _tail_ of the request queue.
TUR is using the 'SG_IO' ioctl, which is added to the head of the
request_queue and hence won't be stalled ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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