[Cake] RHODIUM - nuking blue (for testing)

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

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Given some of the results thus far at various RTTs, and at higher
loads, like the ginormous one georgios just ran, I thought it might be
useful to run a battery of tests with blue disabled.

I haven't gone to the trouble of creating a formal branch - tho if I
did, I'd call it rhodium, as rhodium detectors are used in nuclear
reactors to measure the neutron flux level.

untested-but-compiling-patch attached. I'm busy on a few other things
this week, and it is looking like we'll have to replace the xstats
structure with something smaller to go mainline.

-- 

Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619

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From 56a55081199ed9ee36de8a2806a7c51d5a83a078 Mon Sep 17 00:00:00 2001
From: Dave Taht <dave.taht@gmail.com>
Date: Tue, 5 Dec 2017 11:22:08 -0800
Subject: [PATCH] RHODIUM: disable blue algorithm for testing

This patch disables the blue algorithm so the aqm becomes more
pure codel.
---
 cobalt.h   |  2 ++
 sch_cake.c | 13 ++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/cobalt.h b/cobalt.h
index f10f9db..c1d9dff 100644
--- a/cobalt.h
+++ b/cobalt.h
@@ -126,8 +126,10 @@ struct cobalt_vars {
 	u32		count;
 	u32		rec_inv_sqrt;
 	cobalt_time_t	drop_next;
+#ifndef RHODIUM
 	cobalt_time_t	blue_timer;
 	u32     p_drop;
+#endif
 	bool	dropping;
 	bool    ecn_marked;
 };
diff --git a/sch_cake.c b/sch_cake.c
index 4010388..134c6ca 100644
--- a/sch_cake.c
+++ b/sch_cake.c
@@ -62,6 +62,7 @@
 #else
 #include <net/flow_dissector.h>
 #endif
+#define RHODIUM 1
 #include "cobalt.h"
 
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
@@ -443,6 +444,7 @@ static bool cobalt_queue_full(struct cobalt_vars *vars,
 {
 	bool up = false;
 
+#ifndef RHODIUM
 	if ((now - vars->blue_timer) > p->target) {
 		up = !vars->p_drop;
 		vars->p_drop += p->p_inc;
@@ -450,6 +452,7 @@ static bool cobalt_queue_full(struct cobalt_vars *vars,
 			vars->p_drop = ~0;
 		vars->blue_timer = now;
 	}
+#endif
 	vars->dropping = true;
 	vars->drop_next = now;
 	if (!vars->count)
@@ -467,6 +470,7 @@ static bool cobalt_queue_empty(struct cobalt_vars *vars,
 {
 	bool down = false;
 
+#ifndef RHODIUM
 	if (vars->p_drop && (now - vars->blue_timer) > p->target) {
 		if (vars->p_drop < p->p_dec)
 			vars->p_drop = 0;
@@ -475,6 +479,7 @@ static bool cobalt_queue_empty(struct cobalt_vars *vars,
 		vars->blue_timer = now;
 		down = !vars->p_drop;
 	}
+#endif
 	vars->dropping = false;
 
 	if (vars->count && (now - vars->drop_next) >= 0) {
@@ -559,10 +564,11 @@ static bool cobalt_should_drop(struct cobalt_vars *vars,
 		}
 	}
 
+#ifndef RHODIUM
 	/* Simple BLUE implementation.  Lack of ECN is deliberate. */
 	if (vars->p_drop)
 		drop |= (prandom_u32() < vars->p_drop);
-
+#endif
 	/* Overload the drop_next field as an activity timeout */
 	if (!vars->count)
 		vars->drop_next = now + p->interval;
@@ -1818,8 +1824,13 @@ retry:
 			if (cobalt_queue_empty(&flow->cvars, &b->cparams, now))
 				b->unresponsive_flow_count--;
 
+#ifndef RHODIUM
 			if (flow->cvars.p_drop || flow->cvars.count ||
 			    (now - flow->cvars.drop_next) < 0) {
+#else
+			if (flow->cvars.count ||
+			    (now - flow->cvars.drop_next) < 0) {
+#endif
 				/* keep in the flowchain until the state has
 				 * decayed to rest
 				 */
-- 
2.7.4