netdev - Re: ipgre rss is broken since gro

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Date:	Sun, 9 Dec 2012 15:27:07 -0800
From:	Eric Dumazet <edumazet@...gle.com>
To:	Dmitry Kravkov <dmitry@...adcom.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: ipgre rss is broken since gro

On Sun, Dec 9, 2012 at 12:49 PM, Dmitry Kravkov <dmitry@...adcom.com> wrote:

> for this item: drop_watch does not show any drops (i've disable all
> other interfaces for clear env)
> I will explain a little bit more the setup:
> bnx2x device (under testing) is configured for RSS for IPGRE packets.
> Sending multiple (3) TCP_STREAM causes ip_gre interface to disappear
> packets (even ICMP).
> This is not happening with single TCP_STREAM, or before gro_cell
> introduction.
>
> i was searching for the drops by print-out in ip_gre.c but disappeared
> packets completes this code:
>
> static int ipgre_rcv(struct sk_buff *skb)
> (snip)
>                 printk("%s:%d\n", __FUNCTION__, __LINE__);
>
>                 tstats = this_cpu_ptr(tunnel->dev->tstats);
>                 u64_stats_update_begin(&tstats->syncp);
>                 tstats->rx_packets++;
>                 tstats->rx_bytes += skb->len;
>                 u64_stats_update_end(&tstats->syncp);
>
>                 gro_cells_receive(&tunnel->gro_cells, skb);
>                 return 0;

I dont know, I tried a bnx2x setup, and 100 tcp flows, no special problem.

If you receive a lot of packets on a single RX queue, they might be
dropped because cpu cant cope with the load
(This has nothing to do with GRE or GRO )

cat /proc/net/softnet_stat
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