Re: [Cake] Advantages to tightly tuning latency

[Dave Taht <dave.taht@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1178 bytes --]

On Thu, Apr 23, 2020 at 4:57 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Maxime Bizon <mbizon@freebox.fr> writes:
>
> > On Wednesday 22 Apr 2020 à 07:48:43 (-0700), Dave Taht wrote:
> >
> > Hello,
> >
> >> > Free has been using SFQ since 2005 (if I remember well).
> >> > They announced the wide deployment of SFQ in the free.fr newsgroup.
> >> > Wi-Fi in the free.fr router was not as good though.
> >>
> >> They're working on it. :)
> >
> > yes indeed.
> >
> > Switching to softmac approach, so now mac80211 will do rate control
> > and scheduling (using wake_tx_queue model).
> >
> > for 5ghz, we use ath10k
>
> That is awesome! Please make sure you include the AQL patch for ath10k,
> it really works wonders, as Dave demonstrated:
>
> https://lists.bufferbloat.net/pipermail/make-wifi-fast/2020-March/002721.html

and THIS patch is looking lovely at the higher rates I'm testing at.
Yea, it needs to be more robust, but I'm seeing tcp rtt inflation
of exactly the right buffer size (15ms), on an HT20 or VHT80 link,
where before I'd see 30+ms... (it's nice that flent can plot both tcp
rtt and ping rtt now),
ecn "just works",

[-- Attachment #2: 982-do-codel-more-right.patch --]
[-- Type: text/x-patch, Size: 1767 bytes --]

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index c431722..92ba09b 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -476,10 +476,11 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	sta->sta.max_rc_amsdu_len = IEEE80211_MAX_MPDU_LEN_HT_BA;
 
 	sta->cparams.ce_threshold = CODEL_DISABLED_THRESHOLD;
-	sta->cparams.target = MS2TIME(20);
+	sta->cparams.target = MS2TIME(5);
 	sta->cparams.interval = MS2TIME(100);
 	sta->cparams.ecn = true;
-
+	sta_dbg(sdata, "Codel target, interval %d, %d\n", sta->cparams.target,
+		sta->cparams.interval);
 	sta_dbg(sdata, "Allocated STA %pM\n", sta->sta.addr);
 
 	return sta;
@@ -2468,15 +2469,9 @@ static void sta_update_codel_params(struct sta_info *sta, u32 thr)
 	if (!sta->sdata->local->ops->wake_tx_queue)
 		return;
 
-	if (thr && thr < STA_SLOW_THRESHOLD * sta->local->num_sta) {
-		sta->cparams.target = MS2TIME(50);
-		sta->cparams.interval = MS2TIME(300);
-		sta->cparams.ecn = false;
-	} else {
-		sta->cparams.target = MS2TIME(20);
-		sta->cparams.interval = MS2TIME(100);
-		sta->cparams.ecn = true;
-	}
+	sta->cparams.target = MS2TIME(5);
+	sta->cparams.interval = MS2TIME(100);
+	sta->cparams.ecn = true;
 }
 
 void ieee80211_sta_set_expected_throughput(struct ieee80211_sta *pubsta,
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 535911b..ca50d0a 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1551,7 +1551,7 @@ int ieee80211_txq_setup_flows(struct ieee80211_local *local)
 
 	codel_params_init(&local->cparams);
 	local->cparams.interval = MS2TIME(100);
-	local->cparams.target = MS2TIME(20);
+	local->cparams.target = MS2TIME(5);
 	local->cparams.ecn = true;
 
 	local->cvars = kcalloc(fq->flows_cnt, sizeof(local->cvars[0]),