[Cake] [PATCH net-next] sch_cake: Make gso-splitting configurable from userspace

[Dave Taht]

I should have made that be an RFC. Ah, well.
On Thu, Jul 26, 2018 at 7:45 PM Dave Taht <dave.taht at gmail.com> wrote:
>
> This patch restores cake's deployed behavior at line rate to always
> split gso, and makes gso splitting configurable from userspace.
>
> running cake unlimited (unshaped) at 1gigE, local traffic:
>
> no-split-gso bql limit: 131966
> split-gso bql limit:   ~42392-45420
>
> On this 4 stream test splitting gso apart results in halving the
> observed interpacket latency at no loss in throughput.
>
> Summary of tcp_nup test run 'gso-split' (at 2018-07-26 16:03:51.824728):
>
>  Ping (ms) ICMP :         0.83         0.81 ms              341
>  TCP upload avg :       235.43       235.39 Mbits/s         301
>  TCP upload sum :       941.71       941.56 Mbits/s         301
>  TCP upload::1  :       235.45       235.43 Mbits/s         271
>  TCP upload::2  :       235.45       235.41 Mbits/s         289
>  TCP upload::3  :       235.40       235.40 Mbits/s         288
>  TCP upload::4  :       235.41       235.40 Mbits/s         291
>
> verses
>
> Summary of tcp_nup test run 'no-split-gso' (at 2018-07-26 16:37:23.563960):
>
>                            avg       median          # data pts
>  Ping (ms) ICMP :         1.67         1.73 ms              348
>  TCP upload avg :       234.56       235.37 Mbits/s         301
>  TCP upload sum :       938.24       941.49 Mbits/s         301
>  TCP upload::1  :       234.55       235.38 Mbits/s         285
>  TCP upload::2  :       234.57       235.37 Mbits/s         286
>  TCP upload::3  :       234.58       235.37 Mbits/s         274
>  TCP upload::4  :       234.54       235.42 Mbits/s         288
> ---
>  net/sched/sch_cake.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
> index 539c949..35fc725 100644
> --- a/net/sched/sch_cake.c
> +++ b/net/sched/sch_cake.c
> @@ -80,7 +80,6 @@
>  #define CAKE_QUEUES (1024)
>  #define CAKE_FLOW_MASK 63
>  #define CAKE_FLOW_NAT_FLAG 64
> -#define CAKE_SPLIT_GSO_THRESHOLD (125000000) /* 1Gbps */
>
>  /* struct cobalt_params - contains codel and blue parameters
>   * @interval:  codel initial drop rate
> @@ -2569,10 +2568,12 @@ static int cake_change(struct Qdisc *sch, struct nlattr *opt,
>         if (tb[TCA_CAKE_MEMORY])
>                 q->buffer_config_limit = nla_get_u32(tb[TCA_CAKE_MEMORY]);
>
> -       if (q->rate_bps && q->rate_bps <= CAKE_SPLIT_GSO_THRESHOLD)
> -               q->rate_flags |= CAKE_FLAG_SPLIT_GSO;
> -       else
> -               q->rate_flags &= ~CAKE_FLAG_SPLIT_GSO;
> +       if (tb[TCA_CAKE_SPLIT_GSO]) {
> +               if (!!nla_get_u32(tb[TCA_CAKE_SPLIT_GSO]))
> +                       q->rate_flags |= CAKE_FLAG_SPLIT_GSO;
> +               else
> +                       q->rate_flags &= ~CAKE_FLAG_SPLIT_GSO;
> +       }
>
>         if (q->tins) {
>                 sch_tree_lock(sch);
> @@ -2608,7 +2609,7 @@ static int cake_init(struct Qdisc *sch, struct nlattr *opt,
>         q->target   =   5000; /* 5ms: codel RFC argues
>                                * for 5 to 10% of interval
>                                */
> -
> +       q->rate_flags |= CAKE_FLAG_SPLIT_GSO;
>         q->cur_tin = 0;
>         q->cur_flow  = 0;
>
> --
> 2.7.4
>


-- 

Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619