netdev - Re: Regression on TX throughput when using bonding

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Message-ID: <CAL8zT=icffEiz9MeaNwMtzteQnXiaT4k++s0TPWt5zsnHxFbmw@mail.gmail.com>
Date:	Thu, 14 Jun 2012 12:15:37 +0200
From:	Jean-Michel Hautbois <jhautbois@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: Regression on TX throughput when using bonding

2012/6/14 Eric Dumazet <eric.dumazet@...il.com>:
> On Thu, 2012-06-14 at 11:22 +0200, Eric Dumazet wrote:
>
>> So you are saying that if you make skb_orphan_try() doing nothing, it
>> solves your problem ?
>
> It probably does, if your application does an UDP flood, trying to send
> more than the link bandwidth. I guess only benchmarks workloads ever try
> to do that.
>
> bonding has no way to give congestion back, it has no Qdisc by default.
>
> We probably can defer the skb_orphan_try() for bonding master, a bit
> like the IFF_XMIT_DST_RELEASE
>
>  drivers/net/bonding/bond_main.c |    2 +-
>  include/linux/if.h              |    3 +++
>  net/core/dev.c                  |    5 +++--
>  3 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 2ee8cf9..1b1e9c8 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -4343,7 +4343,7 @@ static void bond_setup(struct net_device *bond_dev)
>        bond_dev->tx_queue_len = 0;
>        bond_dev->flags |= IFF_MASTER|IFF_MULTICAST;
>        bond_dev->priv_flags |= IFF_BONDING;
> -       bond_dev->priv_flags &= ~(IFF_XMIT_DST_RELEASE | IFF_TX_SKB_SHARING);
> +       bond_dev->priv_flags &= ~(IFF_XMIT_DST_RELEASE | IFF_TX_SKB_SHARING | IFF_XMIT_ORPHAN);
>
>        /* At first, we block adding VLANs. That's the only way to
>         * prevent problems that occur when adding VLANs over an
> diff --git a/include/linux/if.h b/include/linux/if.h
> index f995c66..a788e7b 100644
> --- a/include/linux/if.h
> +++ b/include/linux/if.h
> @@ -81,6 +81,9 @@
>  #define IFF_UNICAST_FLT        0x20000         /* Supports unicast filtering   */
>  #define IFF_TEAM_PORT  0x40000         /* device used as team port */
>  #define IFF_SUPP_NOFCS 0x80000         /* device supports sending custom FCS */
> +#define IFF_XMIT_ORPHAN        0x100000        /* dev_hard_start_xmit() is allowed to
> +                                        * orphan skb
> +                                        */
>
>
>  #define IF_GET_IFACE   0x0001          /* for querying only */
> diff --git a/net/core/dev.c b/net/core/dev.c
> index cd09819..3435463 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2193,7 +2193,8 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
>                if (!list_empty(&ptype_all))
>                        dev_queue_xmit_nit(skb, dev);
>
> -               skb_orphan_try(skb);
> +               if (dev->priv_flags & IFF_XMIT_ORPHAN)
> +                       skb_orphan_try(skb);
>
>                features = netif_skb_features(skb);
>
> @@ -5929,7 +5930,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
>        INIT_LIST_HEAD(&dev->napi_list);
>        INIT_LIST_HEAD(&dev->unreg_list);
>        INIT_LIST_HEAD(&dev->link_watch_list);
> -       dev->priv_flags = IFF_XMIT_DST_RELEASE;
> +       dev->priv_flags = IFF_XMIT_DST_RELEASE | IFF_XMIT_ORPHAN;
>        setup(dev);
>
>        dev->num_tx_queues = txqs;
>
>

It works
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