On Thu, 2016-09-22 at 19:34 -0300, Marcelo Ricardo Leitner wrote:
> On Sat, Aug 27, 2016 at 07:37:54AM -0700, Eric Dumazet wrote:
> > +bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
> > +{
> > + u32 limit = sk->sk_rcvbuf + sk->sk_sndbuf;
> ^^^
> ...
> > + if (!skb->data_len)
> > + skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));
> > +
> > + if (unlikely(sk_add_backlog(sk, skb, limit))) {
> ...
> > - } else if (unlikely(sk_add_backlog(sk, skb,
> > - sk->sk_rcvbuf + sk->sk_sndbuf))) {
> ^---- [1]
> > - bh_unlock_sock(sk);
> > - __NET_INC_STATS(net, LINUX_MIB_TCPBACKLOGDROP);
> > + } else if (tcp_add_backlog(sk, skb)) {
>
> Hi Eric, after this patch, do you think we still need to add sk_sndbuf
> as a stretching factor to the backlog here?
>
> It was added by [1] and it was justified that the (s)ack packets were
> just too big for the rx buf size. Maybe this new patch alone is enough
> already, as such packets will have a very small truesize then.
>
> Marcelo
>
> [1] da882c1f2eca ("tcp: sk_add_backlog() is too agressive for TCP")
>
Hi Marcelo
Yes, it is still needed, some drivers provide linear skbs, so the
skb->truesize of ack packets will likely be the same (skb->head points
to a full size frame allocated by the driver)
