diff options
| author | Leslie Monis <lesliemonis@gmail.com> | 2020-03-05 00:26:01 +0530 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-03-04 13:25:55 -0800 |
| commit | 105e808c1da2a2827a4a374ae6e3003249729eec (patch) | |
| tree | e6045369559f0fb426929d5fee0e22303a7d95e7 /net/sched | |
| parent | 220d4ac74ed691033b6fe2bd98dc07d6bdece046 (diff) | |
pie: remove pie_vars->accu_prob_overflows
The variable pie_vars->accu_prob is used as an accumulator for
probability values. Since probabilty values are scaled using the
MAX_PROB macro denoting (2^64 - 1), pie_vars->accu_prob is
likely to overflow as it is of type u64.
The variable pie_vars->accu_prob_overflows counts the number of
times the variable pie_vars->accu_prob overflows.
The MAX_PROB macro needs to be equal to at least (2^39 - 1) in
order to do precise calculations without any underflow. Thus
MAX_PROB can be reduced to (2^56 - 1) without affecting the
precision in calculations drastically. Doing so will eliminate
the need for the variable pie_vars->accu_prob_overflows as the
variable pie_vars->accu_prob will never overflow.
Removing the variable pie_vars->accu_prob_overflows also reduces
the size of the structure pie_vars to exactly 64 bytes.
Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
| -rw-r--r-- | net/sched/sch_fq_pie.c | 1 | ||||
| -rw-r--r-- | net/sched/sch_pie.c | 21 |
2 files changed, 6 insertions, 16 deletions
diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c index 214657eb3dfd..a9da8776bf5b 100644 --- a/net/sched/sch_fq_pie.c +++ b/net/sched/sch_fq_pie.c @@ -189,7 +189,6 @@ static int fq_pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, out: q->stats.dropped++; sel_flow->vars.accu_prob = 0; - sel_flow->vars.accu_prob_overflows = 0; __qdisc_drop(skb, to_free); qdisc_qstats_drop(sch); return NET_XMIT_CN; diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c index 198cfa34a00a..f52442d39bf5 100644 --- a/net/sched/sch_pie.c +++ b/net/sched/sch_pie.c @@ -62,27 +62,19 @@ bool pie_drop_early(struct Qdisc *sch, struct pie_params *params, else local_prob = vars->prob; - if (local_prob == 0) { + if (local_prob == 0) vars->accu_prob = 0; - vars->accu_prob_overflows = 0; - } - - if (local_prob > MAX_PROB - vars->accu_prob) - vars->accu_prob_overflows++; - - vars->accu_prob += local_prob; + else + vars->accu_prob += local_prob; - if (vars->accu_prob_overflows == 0 && - vars->accu_prob < (MAX_PROB / 100) * 85) + if (vars->accu_prob < (MAX_PROB / 100) * 85) return false; - if (vars->accu_prob_overflows == 8 && - vars->accu_prob >= MAX_PROB / 2) + if (vars->accu_prob >= (MAX_PROB / 2) * 17) return true; prandom_bytes(&rnd, 8); - if (rnd < local_prob) { + if ((rnd >> BITS_PER_BYTE) < local_prob) { vars->accu_prob = 0; - vars->accu_prob_overflows = 0; return true; } @@ -129,7 +121,6 @@ static int pie_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch, out: q->stats.dropped++; q->vars.accu_prob = 0; - q->vars.accu_prob_overflows = 0; return qdisc_drop(skb, sch, to_free); } |