Eric Dumazet [off-list ref] wrote:

On Fri, 2015-02-27 at 19:11 -0800, Tom Herbert wrote:

quoted

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index c605d30..d41a034 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h

@@ -252,7 +252,7 @@ struct qdisc_skb_cb {
 	unsigned int		pkt_len;
 	u16			slave_dev_queue_mapping;
 	u16			_pad;
-#define QDISC_CB_PRIV_LEN 20
+#define QDISC_CB_PRIV_LEN 24
 	unsigned char		data[QDISC_CB_PRIV_LEN];
 };
 

This change breaks kernel build : We already are at the cb[] limit.

Please check commit 257117862634d89de33fec74858b1a0ba5ab444b
("net: sched: shrink struct qdisc_skb_cb to 28 bytes")

I've been toying around with reducing skb->cb[] to 44 bytes,
Seems Tom could integrate following patch from my test branch:

http://git.breakpoint.cc/cgit/fw/net-next.git/commit/?h=skb_cb_44_01&id=29d711e1a71244b71940c2d1e346500bef4d6670

It makes sfq use a smaller flow key state.