Re: [Cake] Dropping last_len from stats collection & display.

[Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>]

On 01/06/16 15:00, Jonathan Morton wrote:
>
>> On 1 Jun, 2016, at 14:40, Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk> wrote:
>>
>> Not updating another variable (memory write) for each packet may help cake's CPU usage a little.
>
> I’ll think about this one.
>
> I don’t think it should gate the LEDE merge (nor should it require a stats version bump), since as long as the entry remains in the stats struct, it will simply remain zero if not written.
>
> In future the space could be reused, in which case a version bump would be appropriate.
>
>   - Jonathan Morton
>

Two points/suggestions/alternate perspectives:

Not bumping the version leads to a situation where tc constantly reports 
the last length as zero.  I would suggest that looks 
odd/oversight/wrong.  A version bump at least allows a later tc to know 
not to output a dead value.


I can see your point with regard to the structure size, how about 
re-adding as

u32 __attribute__((used)) last_skblen;  /* V3 and below */

to stop the unused variable warning that would otherwise result.

The other argument I keep having with myself is "none of this has been 
released...yet".  Aren't we still free to break this as we see fit :-)