[dm-devel] [PATCH 2/4] dm stats: support precise timestamps

[Vivek Goyal]

On Tue, Jun 09, 2015 at 05:21:39PM -0400, Mikulas Patocka wrote:

[..]
>  Messages
>  ========
>  
> -    @stats_create <range> <step> [<program_id> [<aux_data>]]
> +    @stats_create <range> <step>
> +    		[<number_of_optional_arguments> <optional_arguments>...]
> +		[<program_id> [<aux_data>]]
>  
>  	Create a new region and return the region_id.
>  
> @@ -48,6 +54,17 @@ Messages
>  	  "/<number_of_areas>" - the range is subdivided into the specified
>  				 number of areas.
>  
> +	<number_of_optional_arguments>
> +	  The number of optional arguments
> +
> +	<optional_arguments>
> +	  The following optional arguments are supported
> +	  precise_timestamps - use precise timer with nanosecond resolution
> +	  	instead of the "jiffies" variable.  When this argument is
> +		used, the resulting times are in nanoseconds instead of
> +		milliseconds.  Precise timestamps are a little bit slower
> +		to obtain than jiffies-based timestamps.
> +

Instead of "precise_timestams" will it make sense to call it
"nanosecond_timestamps" or "ns_timestamps".


>  	<program_id>
>  	  An optional parameter.  A name that uniquely identifies
>  	  the userspace owner of the range.  This groups ranges together

We are adding these new parameters/arguments in between existing parameters.
Will it break any of the existing scritps. Will it make sense to add these
new parameters at the end. It is more intuitive.

Also, I was wondering that why do we need to introduce this notion of
number of optional arguments. Can't we just introduce another optional
parameter [ns_timestamps]. That feels little simpler.

Thanks
Vivek