[dpdk-dev] [PATCH v5] sched: make RED scaling configurable

[Dewar, Alan]

> > > > > diff --git a/lib/librte_sched/rte_red.c 
> > > > > b/lib/librte_sched/rte_red.c
> > > > > +int
> > > > > +rte_red_set_scaling(uint16_t max_red_queue_length) {
> > > > > +	int8_t count;
> > > > > +
> > > > > +	if (rte_red_init_done)
> > > > > +		/**
> > > > > +		 * Can't change the scaling once the red table has been
> > > > > +		 * computed.
> > > > > +		 */
> > > > > +		return -1;
> > > >
> > > > Is there a reason why we cannot simply reset the scaling here?
> > >
> > > Actually we could, but I was originally thinking that you might be 
> > > happier keeping with a one-time RED initialization function, but 
> > > then had to introduce the rte_reset_red_scaling function for the 
> > > unit-tests. I'm happy
> > to
> > > do RED reinitialization here, if you are.
> > >
> > 
> > Hi Alan,
> > 
> > What is the intention of the new rte_red_set_scaling() function?
> > 	1. Is it to be called only once, before any RED object gets created?
> > 	2. Is it possible to call it post-init, but in this case any RED 
> > object already created are not impacted (they continue to work)?
> > 
> > If the answer is 2, then yes, we could simply drop the 
> > __rte_red_reset() and do the RED globals reset as part of the 
> > rte_red_set_scaling() function transparently.
> > 
> > If the answer is 1, then we probably need to keep your approach: we 
> > need a global rte_red_init_done flag, and rte_red_set_scaling() could 
> > only be called at init time before any red objects are created.
> > 
> > I probably need to spend more time assessing all the code implications.
> > 
> > Regards,
> > Cristian
>
> Hi Alan,
>
> After talking to Tomasz, we agreed that 2. Is not an option, as any previously created red object will be broken.
>
> So 1. Is the right answer, therefore this function can be called only once and only before any red objects are created. So, IMO we should do this:
-when rte_red_init_done is true, we need to return error -when rte_red_init_done is false, we need to perform red initialization and set this flag
>
> Agree?

Yes, as long as you're happy with keeping __rte_red_reset for the unit-tests.

> Please also add a comment in the Doxygen description of rte_red_set_caling() in the rte_red.h file, stating that this function can be called only once and only before any red objects are created.

Will do.

> Regards,
> Cristian