Commit Graph

4 Commits

Author SHA1 Message Date
David S. Miller 16bda13d90 net: Make qdisc_skb_cb upper size bound explicit.
Just like skb->cb[], so that qdisc_skb_cb can be encapsulated inside
of other data structures.

This is intended to be used by IPoIB so that it can remember
addressing information stored at hard_header_ops->create() time that
it can fetch when the packet gets to the transmit routine.

Signed-off-by: David S. Miller <davem@davemloft.net>
2012-02-09 13:50:34 -05:00
Eric Dumazet a00bd469b6 sch_sfb: use skb_flow_dissect()
Current SFB double hashing is not fulfilling SFB theory, if two flows
share same rxhash value.

Using skb_flow_dissect() permits to really have better hash dispersion,
and get tunnelling support as well.

Double hashing point was mentioned by Florian Westphal

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-11-28 19:09:28 -05:00
Eric Dumazet 363437f40a net_sched: sfb: optimize enqueue on full queue
In case SFB queue is full (hard limit reached), there is no point
spending time to compute hash and maximum qlen/p_mark.

We instead just early drop packet.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-08-26 12:55:18 -04:00
Eric Dumazet e13e02a3c6 net_sched: SFB flow scheduler
This is the Stochastic Fair Blue scheduler, based on work from :

W. Feng, D. Kandlur, D. Saha, K. Shin. Blue: A New Class of Active Queue
Management Algorithms. U. Michigan CSE-TR-387-99, April 1999.

http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf

This implementation is based on work done by Juliusz Chroboczek

General SFB algorithm can be found in figure 14, page 15:

B[l][n] : L x N array of bins (L levels, N bins per level)
enqueue()
Calculate hash function values h{0}, h{1}, .. h{L-1}
Update bins at each level
for i = 0 to L - 1
   if (B[i][h{i}].qlen > bin_size)
      B[i][h{i}].p_mark += p_increment;
   else if (B[i][h{i}].qlen == 0)
      B[i][h{i}].p_mark -= p_decrement;
p_min = min(B[0][h{0}].p_mark ... B[L-1][h{L-1}].p_mark);
if (p_min == 1.0)
    ratelimit();
else
    mark/drop with probabilty p_min;

I did the adaptation of Juliusz code to meet current kernel standards,
and various changes to address previous comments :

http://thread.gmane.org/gmane.linux.network/90225
http://thread.gmane.org/gmane.linux.network/90375

Default flow classifier is the rxhash introduced by RPS in 2.6.35, but
we can use an external flow classifier if wanted.

tc qdisc add dev $DEV parent 1:11 handle 11:  \
        est 0.5sec 2sec sfb limit 128

tc filter add dev $DEV protocol ip parent 11: handle 3 \
        flow hash keys dst divisor 1024

Notes:

1) SFB default child qdisc is pfifo_fast. It can be changed by another
qdisc but a child qdisc MUST not drop a packet previously queued. This
is because SFB needs to handle a dequeued packet in order to maintain
its virtual queue states. pfifo_head_drop or CHOKe should not be used.

2) ECN is enabled by default, unlike RED/CHOKe/GRED

With help from Patrick McHardy & Andi Kleen

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Juliusz Chroboczek <Juliusz.Chroboczek@pps.jussieu.fr>
CC: Stephen Hemminger <shemminger@vyatta.com>
CC: Patrick McHardy <kaber@trash.net>
CC: Andi Kleen <andi@firstfloor.org>
CC: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-02-23 14:05:11 -08:00