sch_red: generalize accurate MAX_P support to RED/GRED/CHOKE
Now RED uses a Q0.32 number to store max_p (max probability), allow
RED/GRED/CHOKE to use/report full resolution at config/dump time.
Old tc binaries are non aware of new attributes, and still set/get Plog.
New tc binary set/get both Plog and max_p for backward compatibility,
they display "probability value" if they get max_p from new kernels.
# tc -d qdisc show dev ...
...
qdisc red 10: parent 1:1 limit 360Kb min 30Kb max 90Kb ecn ewma 5
probability 0.09 Scell_log 15
Make sure we avoid potential divides by 0 in reciprocal_value(), if
(max_th - min_th) is big.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/red.h b/include/net/red.h
index 24606b2..ef715a1 100644
--- a/include/net/red.h
+++ b/include/net/red.h
@@ -155,9 +155,10 @@
static inline void red_set_parms(struct red_parms *p,
u32 qth_min, u32 qth_max, u8 Wlog, u8 Plog,
- u8 Scell_log, u8 *stab)
+ u8 Scell_log, u8 *stab, u32 max_P)
{
int delta = qth_max - qth_min;
+ u32 max_p_delta;
/* Reset average queue length, the value is strictly bound
* to the parameters below, reseting hurts a bit but leaving
@@ -173,10 +174,14 @@
if (delta < 0)
delta = 1;
p->qth_delta = delta;
- p->max_P = red_maxp(Plog);
- p->max_P *= delta; /* max_P = (qth_max-qth_min)/2^Plog */
-
- p->max_P_reciprocal = reciprocal_value(p->max_P / delta);
+ if (!max_P) {
+ max_P = red_maxp(Plog);
+ max_P *= delta; /* max_P = (qth_max - qth_min)/2^Plog */
+ }
+ p->max_P = max_P;
+ max_p_delta = max_P / delta;
+ max_p_delta = max(max_p_delta, 1U);
+ p->max_P_reciprocal = reciprocal_value(max_p_delta);
/* RED Adaptative target :
* [min_th + 0.4*(min_th - max_th),
@@ -380,6 +385,7 @@
p->max_P = (p->max_P/10)*9; /* maxp = maxp * Beta */
max_p_delta = DIV_ROUND_CLOSEST(p->max_P, p->qth_delta);
+ max_p_delta = max(max_p_delta, 1U);
p->max_P_reciprocal = reciprocal_value(max_p_delta);
}
#endif
