From 3e8b1eb21c8b9806928000bf733e5762a64a7f72 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@openwrt.org>
Date: Sat, 16 Mar 2013 17:00:25 +0100
Subject: [PATCH] mac80211/minstrel_ht: improve rate selection stability
Under load, otherwise stable rates can easily fluctuate because of
collisions. In my tests on a clean channel, the success probability of
the max throughput rate often stays somewhere between 90% and 100% under
load. This can cause some unnecessary switching to lower rates.
This patch improves stability by treating success probability values
between 90% and 100% the same.
In my tests on a 3x3 HT20 link with lots of TCP traffic, it improves the
average throughput by a few mbit/s.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
net/mac80211/rc80211_minstrel_ht.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/net/mac80211/rc80211_minstrel_ht.c b/net/mac80211/rc80211_minstrel_ht.c
index 749552bdcfe1e..90499c4217026 100644
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -202,14 +202,23 @@ minstrel_ht_calc_tp(struct minstrel_ht_sta *mi, int group, int rate)
struct minstrel_rate_stats *mr;
unsigned int nsecs = 0;
unsigned int tp;
+ unsigned int prob;
mr = &mi->groups[group].rates[rate];
+ prob = mr->probability;
- if (mr->probability < MINSTREL_FRAC(1, 10)) {
+ if (prob < MINSTREL_FRAC(1, 10)) {
mr->cur_tp = 0;
return;
}
+ /*
+ * For the throughput calculation, limit the probability value to 90% to
+ * account for collision related packet error rate fluctuation
+ */
+ if (prob > MINSTREL_FRAC(9, 10))
+ prob = MINSTREL_FRAC(9, 10);
+
if (group != MINSTREL_CCK_GROUP)
nsecs = 1000 * mi->overhead / MINSTREL_TRUNC(mi->avg_ampdu_len);
--
2.30.2