On Wed, 31 Oct 2018 21:49:29 +0530
Leslie Monis <lesliemo...@gmail.com> wrote:
> From: "Mohit P. Tahiliani" <tahili...@nitk.edu.in>
>
> The update in drop probability depends on the parameters
> alpha and beta, which in turn reflect the current congestion
> level. However, the previous if-else cases were recommended
> when the supported bandwidth was up to 12 Mbps but, current
> data links support a much higher bandwidth, and the
> requirement for more bandwidth is in never-ending demand.
> Hence, RFC 8033 suggests using more if-else cases for better
> fine-tuning of parameters alpha and beta in order to control
> the congestion as much as possible.
>
> Signed-off-by: Mohit P. Tahiliani <tahili...@nitk.edu.in>
> Signed-off-by: Dhaval Khandla <dhavaljkhandl...@gmail.com>
> Signed-off-by: Hrishikesh Hiraskar <hrishihiras...@gmail.com>
> Signed-off-by: Manish Kumar B <bmanish15...@gmail.com>
> Signed-off-by: Sachin D. Patil <sdp.sac...@gmail.com>
> Signed-off-by: Leslie Monis <lesliemo...@gmail.com>
> ---
> net/sched/sch_pie.c | 26 +++++++++++++++++++++++---
> 1 file changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
> index f4e189a..c84e91e 100644
> --- a/net/sched/sch_pie.c
> +++ b/net/sched/sch_pie.c
> @@ -343,10 +343,30 @@ static void calculate_probability(struct Qdisc *sch)
> * appropriately 2) scaling down by 16 to come to 0-2 range.
> * Please see paper for details.
> *
> - * We scale alpha and beta differently depending on whether we are in
> - * light, medium or high dropping mode.
> + * We scale alpha and beta differently depending on how heavy the
> + * congestion is.
> */
> - if (q->vars.prob < MAX_PROB / 100) {
> + if (q->vars.prob < MAX_PROB / 1000000) {
> + alpha =
> + (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 15;
> + beta =
> + (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 15;
> + } else if (q->vars.prob < MAX_PROB / 100000) {
> + alpha =
> + (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 13;
> + beta =
> + (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 13;
> + } else if (q->vars.prob < MAX_PROB / 10000) {
> + alpha =
> + (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 11;
> + beta =
> + (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 11;
> + } else if (q->vars.prob < MAX_PROB / 1000) {
> + alpha =
> + (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 9;
> + beta =
> + (q->params.beta * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 9;
> + } else if (q->vars.prob < MAX_PROB / 100) {
> alpha =
> (q->params.alpha * (MAX_PROB / PSCHED_TICKS_PER_SEC)) >> 7;
> beta =
Seems like the if/else chain is getting long in the tail. Maybe a loop
or table driven approach would be clearer.
