From: Leslie Monis
> Sent: 27 February 2019 01:00
> Use div_u64() to resolve build failures on 32-bit platforms.
>
> Fixes: 3f7ae5f3dc52 ("net: sched: pie: add more cases to auto-tune alpha and
> beta")
> Signed-off-by: Leslie Monis <[email protected]>
> ---
> net/sched/sch_pie.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
> index 4c0670b6aec1..f93cfe034c72 100644
> --- a/net/sched/sch_pie.c
> +++ b/net/sched/sch_pie.c
> @@ -429,7 +429,7 @@ static void calculate_probability(struct Qdisc *sch)
> */
>
> if (qdelay == 0 && qdelay_old == 0 && update_prob)
> - q->vars.prob = (q->vars.prob * 98) / 100;
> + q->vars.prob = 98 * div_u64(q->vars.prob, 100);
This has significantly different rounding after the change.
The result for small values is very different.
The alterative:
q->vars.prob -= div_u64(q->vars.prob, 50);
is much nearer to the original - but never goes to zero.
If the 98% decay factor isn't critical then you could remove
1/64th or 1/32nd + 1/16th to avoid the slow division.
David
-
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