Re: [PATCH v2] net/sched: sch_cake: skip redundant cake_mq rate updates

[Paolo Abeni]

On 10/27/26 05:32, Shubhang Kaushik (Ampere) wrote:
> cake_mq periodically counts active child qdiscs in cake_dequeue() and
> derives an effective per-child shaper rate. cake_dequeue() currently
> reconfigures every tin after each scan, even when that effective rate
> is unchanged.
>
> The dequeue-time call chain is:
>
>    cake_dequeue()
>      -> cake_configure_rates(..., true)
>        -> cake_config_*()
>          -> cake_set_rate()
>
> With rate_adjust=true, cake_set_rate() only refreshes rate-derived
> state. Tin 0 records the unscaled rate argument in every supported
> CAKE tin mode, so its installed rate identifies whether this call chain
> would change any state.
>
> Skip the reconfiguration when the effective rate is already installed,
> while continuing to update the activity-sampling timestamp and
> active-queue statistic.
>
> Fixes: 1bddd758bac2 ("net/sched: sch_cake: share shaper state across sub-instances of cake_mq")
> Signed-off-by: Shubhang Kaushik (Ampere) <sh@xxxxxxxxxx>
IMHO this is borderline material for 'net'. Was any regression visible on
top of 1bddd758bac2, e.g. in term of CPU usage?

/P