Re: [PATCH iwl-next v3 7/7] ice: Add tracepoint for adding and removing switch rules

[Simon Horman <horms@kernel.org>]

On Thu, Jun 27, 2024 at 04:55:47PM +0200, Marcin Szycik wrote:
> Track the number of rules and recipes added to switch. Add a tracepoint to
> ice_aq_sw_rules(), which shows both rule and recipe count. This information
> can be helpful when designing a set of rules to program to the hardware, as
> it shows where the practical limit is. Actual limits are known (64 recipes,
> 32k rules), but it's hard to translate these values to how many rules the
> *user* can actually create, because of extra metadata being implicitly
> added, and recipe/rule chaining. Chaining combines several recipes/rules to
> create a larger recipe/rule, so one large rule added by the user might
> actually consume multiple rules from hardware perspective.
> 
> Rule counter is simply incremented/decremented in ice_aq_sw_rules(), since
> all rules are added or removed via it.
> 
> Counting recipes is harder, as recipes can't be removed (only overwritten).
> Recipes added via ice_aq_add_recipe() could end up being unused, when
> there is an error in later stages of rule creation. Instead, track the
> allocation and freeing of recipes, which should reflect the actual usage of
> recipes (if something fails after recipe(s) were created, caller should
> free them). Also, a number of recipes are loaded from NVM by default -
> initialize the recipe counter with the number of these recipes on switch
> initialization.
> 
> Example configuration:
>   cd /sys/kernel/tracing
>   echo function > current_tracer
>   echo ice_aq_sw_rules > set_ftrace_filter
>   echo ice_aq_sw_rules > set_event
>   echo 1 > tracing_on
>   cat trace
> 
> Example output:
>   tc-4097    [069] ...1.   787.595536: ice_aq_sw_rules <-ice_rem_adv_rule
>   tc-4097    [069] .....   787.595705: ice_aq_sw_rules: rules=9 recipes=15
>   tc-4098    [057] ...1.   787.652033: ice_aq_sw_rules <-ice_add_adv_rule
>   tc-4098    [057] .....   787.652201: ice_aq_sw_rules: rules=10 recipes=16
> 
> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
> Signed-off-by: Marcin Szycik <marcin.szycik@linux.intel.com>

Reviewed-by: Simon Horman <horms@kernel.org>