pkt_sched: HTB scheduler, change default hysteresis mode to off.

The HTB hysteresis mode reduce the CPU load, but at the
cost of scheduling accuracy.

On ADSL links (512 kbit/s upstream), this inaccuracy introduce
significant jitter, enought to disturbe VoIP.  For details see my
masters thesis (http://www.adsl-optimizer.dk/thesis/), chapter 7,
section 7.3.1, pp 69-70.

Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Acked-by: Martin Devera <devik@cdi.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 5bc1ed4901800af63fc1255ba1f5eecbbe8368de..9134f029ee0f20534d05eba09abe0e84a2e0a712 100644 (file)
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -53,7 +53,7 @@
 */
 
 #define HTB_HSIZE 16           /* classid hash size */
-#define HTB_HYSTERESIS 1       /* whether to use mode hysteresis for speedup */
+#define HTB_HYSTERESIS 0       /* whether to use mode hysteresis for speedup */
 #define HTB_VER 0x30011                /* major must be matched with number suplied by TC as version */
 
 #if HTB_VER >> 16 != TC_HTB_PROTOVER