netdev - Re: [PATCH net-next 0/9] mlx4: order-0 allocations and page recycling

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Message-ID: <1486569156.7793.79.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 08 Feb 2017 07:52:36 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Tariq Toukan <ttoukan.linux@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Martin KaFai Lau <kafai@...com>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH net-next 0/9] mlx4: order-0 allocations and page
 recycling

On Wed, 2017-02-08 at 11:02 +0200, Tariq Toukan wrote:
> 
> On 07/02/2017 5:50 PM, Tariq Toukan wrote:
> > Hi Eric,
> >
> > Thanks for your series.
> >
> > On 07/02/2017 5:02 AM, Eric Dumazet wrote:
> >> As mentioned half a year ago, we better switch mlx4 driver to order-0
> >> allocations and page recycling.
> >>
> >> This reduces vulnerability surface thanks to better skb->truesize 
> >> tracking
> >> and provides better performance in most cases.
> > The series makes significant change in the RX data-path, that requires 
> > deeper checks, in addition to code review.
> > We applied your series and started running both our functional and 
> > performance regression.
> > We will have results by tomorrow morning, and will analyze them during 
> > the day. I'll update about that.
> We hit a kernel panic when running traffic after configuring a large MTU 
> (9000).
> I will take deeper look into this soon and will keep you updated.

Hmm... I saw a typo for XDP, but not for the non XDP path...

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
index 8f16ec8dfadd0f95646c498c14d53f7266a0..e572e175edfe0f7392b9833b5b3f867fd6db 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
@@ -132,7 +132,7 @@ static int mlx4_en_prepare_rx_desc(const struct mlx4_en_priv *priv,
                                        (index << priv->log_rx_info);
 
        if (ring->page_cache.index > 0) {
-               if (frags[0].page) {
+               if (!frags[0].page) {
                        ring->page_cache.index--;
                        frags[0].page = ring->page_cache.buf[ring->page_cache.index].page;
                        frags[0].dma  = ring->page_cache.buf[ring->page_cache.index].dma;