Re: ECN + pfifo_fast borked? (Was Re: [Bloat] shaper team forming up)
From: Eric Dumazet <hidden>
Date: 2011-03-15 18:28:42
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
Le mardi 15 mars 2011 à 19:09 +0200, Jonathan Morton a écrit :
On 15 Mar, 2011, at 8:15 am, Eric Dumazet wrote:quoted
band 0 : high priority packets (like now) band 1 : (old band 1, ECN capable flows) band 2 : (old band 1, no ECN flows) band 3 : low priority packets (old band 2)This seems good to me. It would provide a concrete (if minor) enticement to turn ECN on.
Here is a patch to implement that, on top of net-next-2.6 git tree qdisc pfifo_fast 0: dev eth1 root refcnt 2 bands 4 priomap 2 1 3 3 2 3 0 0 2 2 2 2 2 2 2 2 Sent 168 bytes 2 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index c84b659..95ddf54 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c@@ -412,19 +412,39 @@ static struct Qdisc noqueue_qdisc = { }; -static const u8 prio2band[TC_PRIO_MAX + 1] = { - 1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1 +/* 4-band FIFO queue: old style, but should be a bit faster than + generic prio+fifo combination. + */ + +enum { + BAND_HIGH_PRIO, + BAND_MEDIUM_ECN_PRIO, + BAND_MEDIUM_PRIO, + BAND_LOW_PRIO, + + PFIFO_FAST_BANDS }; -/* 3-band FIFO queue: old style, but should be a bit faster than - generic prio+fifo combination. +/* + * We give a litle incent to ECN flows */ +static const u8 prio2band[TC_PRIO_MAX + 1] = { + [TC_PRIO_BESTEFFORT] = BAND_MEDIUM_PRIO, + [TC_PRIO_FILLER] = BAND_MEDIUM_ECN_PRIO, + [TC_PRIO_BULK] = BAND_LOW_PRIO, + [TC_PRIO_BULK + 1] = BAND_LOW_PRIO, + [TC_PRIO_INTERACTIVE_BULK] = BAND_MEDIUM_PRIO, + [TC_PRIO_INTERACTIVE_BULK + 1] = BAND_LOW_PRIO, + [TC_PRIO_INTERACTIVE] = BAND_HIGH_PRIO, + [TC_PRIO_CONTROL] = BAND_HIGH_PRIO, + + [TC_PRIO_CONTROL+1 ... TC_PRIO_MAX] = BAND_MEDIUM_PRIO, +}; -#define PFIFO_FAST_BANDS 3 /* * Private data for a pfifo_fast scheduler containing: - * - queues for the three band + * - queues for the four bands * - bitmap indicating which of the bands contain skbs */ struct pfifo_fast_priv {
@@ -436,9 +456,13 @@ struct pfifo_fast_priv { * Convert a bitmap to the first band number where an skb is queued, where: * bitmap=0 means there are no skbs on any band. * bitmap=1 means there is an skb on band 0. - * bitmap=7 means there are skbs on all 3 bands, etc. + * bitmap=2 means there is an skb on band 1. + * bitmap=15 means there are skbs on all 4 bands. */ -static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0}; +static const int bitmap2band[1 << PFIFO_FAST_BANDS] = { + -1, 0, 1, 0, 2, 0, 1, 0, + 3, 0, 1, 0, 2, 0, 1, 0 +}; static inline struct sk_buff_head *band2list(struct pfifo_fast_priv *priv, int band)