This patch tweaks the heuristic RA is using to decide whether enough
statistics have been gathered for a candidate Tx rate. The goal is to
avoid Tx rate choices that might turn out to be too optimistic.
In my testing RA now scales upwards a little bit more slowly while the
distance towards the AP is decreasing. The difference is not huge and
taking the extra time to gather more reliable stats should be worth it.
In practice this only affects the case where we probe upwards. If the
current Tx rate starts seeing loss we will still scale down very quickly.
Tests on iwn, iwm, and athn would be appreciated.
This patch is based on a larger collection of patches by Christian Ehrhardt.
I have made stylistic tweaks for consistency.
diff a9cfc08b1ea80b0c0dc35851c61760cf3d3657ba /usr/src
blob - ec419b8e52930370c9fb4ced48fca3382243b9d6
file + sys/net80211/ieee80211_ra.c
--- sys/net80211/ieee80211_ra.c
+++ sys/net80211/ieee80211_ra.c
@@ -41,8 +41,6 @@ void ieee80211_ra_probe_next_rateset(struct ieee80211_
struct ieee80211_node *, const struct ieee80211_ht_rateset *);
int ieee80211_ra_next_mcs(struct ieee80211_ra_node *,
struct ieee80211_node *);
-int ieee80211_ra_probe_valid(struct ieee80211_ra_node *,
- struct ieee80211_node *);
void ieee80211_ra_probe_done(struct ieee80211_ra_node *);
int ieee80211_ra_intra_mode_ra_finished(
struct ieee80211_ra_node *, struct ieee80211_node *);
@@ -57,6 +55,7 @@ void ieee80211_ra_probe_next_rate(struct ieee80211_ra_
int ieee80211_ra_valid_tx_mcs(struct ieee80211com *, int);
uint32_t ieee80211_ra_valid_rates(struct ieee80211com *,
struct ieee80211_node *);
+int ieee80211_ra_probe_valid(struct ieee80211_ra_goodput_stats *);
/* We use fixed point arithmetic with 64 bit integers. */
#define RA_FP_SHIFT 21
@@ -155,12 +154,6 @@ ieee80211_ra_get_txrate(int mcs, int sgi20)
/* A rate's goodput has to be at least this much larger to be "better". */
#define IEEE80211_RA_RATE_THRESHOLD (RA_FP_1 / 64) /* ~ 0.015 */
-/* Number of (sub-)frames which render a probe valid. */
-#define IEEE80211_RA_MIN_PROBE_FRAMES 8
-
-/* Number of Tx retries which, alternatively, render a probe valid. */
-#define IEEE80211_RA_MAX_PROBE_RETRIES 4
-
int
ieee80211_ra_next_lower_intra_rate(struct ieee80211_ra_node *rn,
struct ieee80211_node *ni)
@@ -345,13 +338,6 @@ ieee80211_ra_next_mcs(struct ieee80211_ra_node *rn,
return next;
}
-int
-ieee80211_ra_probe_valid(struct ieee80211_ra_node *rn,
- struct ieee80211_node *ni)
-{
- return rn->valid_probes & (1UL << ni->ni_txmcs);
-}
-
void
ieee80211_ra_probe_clear(struct ieee80211_ra_node *rn,
struct ieee80211_node *ni)
@@ -536,6 +522,21 @@ ieee80211_ra_valid_rates(struct ieee80211com *ic, stru
return valid_mcs;
}
+int
+ieee80211_ra_probe_valid(struct ieee80211_ra_goodput_stats *g)
+{
+ /* 128 packets make up a valid probe in any case. */
+ if (g->nprobe_pkts >= 128)
+ return 1;
+
+ /* 8 packets with > 75% loss make a valid probe, too. */
+ if (g->nprobe_pkts >= 8 &&
+ g->nprobe_pkts - g->nprobe_fail < g->nprobe_pkts / 4)
+ return 1;
+
+ return 0;
+}
+
void
ieee80211_ra_add_stats_ht(struct ieee80211_ra_node *rn,
struct ieee80211com *ic, struct ieee80211_node *ni,
@@ -562,11 +563,11 @@ ieee80211_ra_add_stats_ht(struct ieee80211_ra_node *rn
g->nprobe_pkts += total;
g->nprobe_fail += fail;
- if (g->nprobe_pkts < IEEE80211_RA_MIN_PROBE_FRAMES &&
- g->nprobe_fail < IEEE80211_RA_MAX_PROBE_RETRIES) {
+ if (!ieee80211_ra_probe_valid(g)) {
splx(s);
return;
}
+ rn->valid_probes |= 1U << mcs;
if (g->nprobe_fail > g->nprobe_pkts) {
DPRINTF(("%s fail %u > pkts %u\n",
@@ -577,7 +578,6 @@ ieee80211_ra_add_stats_ht(struct ieee80211_ra_node *rn
sfer = g->nprobe_fail << RA_FP_SHIFT;
sfer /= g->nprobe_pkts;
- rn->valid_probes |= 1U << mcs;
g->nprobe_fail = 0;
g->nprobe_pkts = 0;
@@ -615,7 +615,7 @@ ieee80211_ra_choose(struct ieee80211_ra_node *rn, stru
if (rn->probing) {
/* Probe another rate or settle at the best rate. */
- if (!ieee80211_ra_probe_valid(rn, ni)) {
+ if (!(rn->valid_probes & (1UL << ni->ni_txmcs))) {
splx(s);
return;
}
