Eric Lee / smarc-fsl-linux-kernel

29 Nov, 2011

1 commit

  • a00bd469b   sch_sfb: use skb_flow_dissect() ... Browse Code »

    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
    Signed-off-by: David S. Miller

    Eric Dumazet
     

27 Aug, 2011

1 commit

24 Feb, 2011

1 commit

  • e13e02a3c   net_sched: SFB flow scheduler ... Browse Code »

    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
    CC: Juliusz Chroboczek
    CC: Stephen Hemminger
    CC: Patrick McHardy
    CC: Andi Kleen
    CC: John W. Linville
    Signed-off-by: David S. Miller

    Eric Dumazet