netdev - Re: [bpf-next V1 PATCH 8/8] bpf/xdp: devmap can avoid calling ndo_xdp

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Message-ID: <CAPhsuW7rV61_8xLhQmLRLO0Ak9Y+D=o5ytonwjsQNkVCiJ-Btg@mail.gmail.com>
Date:   Wed, 30 May 2018 15:06:27 -0700
From:   Song Liu <liu.song.a23@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Networking <netdev@...r.kernel.org>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        makita.toshiaki@....ntt.co.jp
Subject: Re: [bpf-next V1 PATCH 8/8] bpf/xdp: devmap can avoid calling ndo_xdp_flush

On Wed, May 30, 2018 at 11:01 AM, Jesper Dangaard Brouer
<brouer@...hat.com> wrote:
> The XDP_REDIRECT map devmap can avoid using ndo_xdp_flush, by instead
> instructing ndo_xdp_xmit to flush via XDP_XMIT_FLUSH flag in
> appropriate places.
>
> Notice after this patch it is possible to remove ndo_xdp_flush
> completely, as this is the last user of ndo_xdp_flush. This is left
> for later patches, to keep driver changes separate.
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> ---
>  kernel/bpf/devmap.c |   20 +++++++-------------
>  1 file changed, 7 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index 04fbd75a5274..9c846a7a8cff 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -217,7 +217,7 @@ void __dev_map_insert_ctx(struct bpf_map *map, u32 bit)
>  }
>
>  static int bq_xmit_all(struct bpf_dtab_netdev *obj,
> -                        struct xdp_bulk_queue *bq)
> +                      struct xdp_bulk_queue *bq, bool flush)

How about we use "int flags" instead of "bool flush" for easier extension?

Thanks,
Song

>  {
>         struct net_device *dev = obj->dev;
>         int sent = 0, drops = 0, err = 0;
> @@ -232,7 +232,8 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
>                 prefetch(xdpf);
>         }
>
> -       sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, 0);
> +       sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q,
> +                                            flush ? XDP_XMIT_FLUSH : 0);
>         if (sent < 0) {
>                 err = sent;
>                 sent = 0;
> @@ -276,7 +277,6 @@ void __dev_map_flush(struct bpf_map *map)
>         for_each_set_bit(bit, bitmap, map->max_entries) {
>                 struct bpf_dtab_netdev *dev = READ_ONCE(dtab->netdev_map[bit]);
>                 struct xdp_bulk_queue *bq;
> -               struct net_device *netdev;
>
>                 /* This is possible if the dev entry is removed by user space
>                  * between xdp redirect and flush op.
> @@ -287,10 +287,7 @@ void __dev_map_flush(struct bpf_map *map)
>                 __clear_bit(bit, bitmap);
>
>                 bq = this_cpu_ptr(dev->bulkq);
> -               bq_xmit_all(dev, bq);
> -               netdev = dev->dev;
> -               if (likely(netdev->netdev_ops->ndo_xdp_flush))
> -                       netdev->netdev_ops->ndo_xdp_flush(netdev);
> +               bq_xmit_all(dev, bq, true);
>         }
>  }
>
> @@ -320,7 +317,7 @@ static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf,
>         struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);
>
>         if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
> -               bq_xmit_all(obj, bq);
> +               bq_xmit_all(obj, bq, false);
>
>         /* Ingress dev_rx will be the same for all xdp_frame's in
>          * bulk_queue, because bq stored per-CPU and must be flushed
> @@ -359,8 +356,7 @@ static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
>
>  static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
>  {
> -       if (dev->dev->netdev_ops->ndo_xdp_flush) {
> -               struct net_device *fl = dev->dev;
> +       if (dev->dev->netdev_ops->ndo_xdp_xmit) {
>                 struct xdp_bulk_queue *bq;
>                 unsigned long *bitmap;
>
> @@ -371,9 +367,7 @@ static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
>                         __clear_bit(dev->bit, bitmap);
>
>                         bq = per_cpu_ptr(dev->bulkq, cpu);
> -                       bq_xmit_all(dev, bq);
> -
> -                       fl->netdev_ops->ndo_xdp_flush(dev->dev);
> +                       bq_xmit_all(dev, bq, true);
>                 }
>         }
>  }
>