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authorLeslie Monis <lesliemonis@gmail.com>2020-03-05 00:26:01 +0530
committerDavid S. Miller <davem@davemloft.net>2020-03-04 13:25:55 -0800
commit105e808c1da2a2827a4a374ae6e3003249729eec (patch)
treee6045369559f0fb426929d5fee0e22303a7d95e7 /net
parent220d4ac74ed691033b6fe2bd98dc07d6bdece046 (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')
-rw-r--r--net/sched/sch_fq_pie.c1
-rw-r--r--net/sched/sch_pie.c21
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);
}