netdev - Re: [RFC PATCH 4/5] mlx4: add support for fast rx drop bpf program

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Message-ID: <20160403061536.GD21980@gmail.com>
Date:	Sat, 2 Apr 2016 23:15:38 -0700
From:	Brenden Blanco <bblanco@...mgrid.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, tom@...bertland.com,
	alexei.starovoitov@...il.com, ogerlitz@...lanox.com,
	daniel@...earbox.net, john.fastabend@...il.com, brouer@...hat.com
Subject: Re: [RFC PATCH 4/5] mlx4: add support for fast rx drop bpf program

On Fri, Apr 01, 2016 at 07:08:31PM -0700, Eric Dumazet wrote:
[...]
> 
> 
> 1) mlx4 can use multiple fragments (priv->num_frags) to hold an Ethernet
> frame. 
> 
> Still you pass a single fragment but total 'length' here : BPF program
> can read past the end of this first fragment and panic the box.
> 
> Please take a look at mlx4_en_complete_rx_desc() and you'll see what I
> mean.
Sure, I will do some reading. Jesper also raised the issue after you
did. Please let me know what you think of the proposals.
> 
> 2) priv->stats.rx_dropped is shared by all the RX queues -> false
> sharing.
> 
>    This is probably the right time to add a rx_dropped field in struct
> mlx4_en_rx_ring since you guys want to drop 14 Mpps, and 50 Mpps on
> higher speed links.
> 
This sounds reasonable! Will look into it for the next spin.