netdev - Re: Bad XDP performance with mlx5

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Message-Id: <20190531.110050.517935401011629843.davem@davemloft.net>
Date:   Fri, 31 May 2019 11:00:50 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     brouer@...hat.com
Cc:     barbette@....se, xdp-newbies@...r.kernel.org, toke@...hat.com,
        saeedm@...lanox.com, leonro@...lanox.com, tariqt@...lanox.com,
        netdev@...r.kernel.org
Subject: Re: Bad XDP performance with mlx5

From: Jesper Dangaard Brouer <brouer@...hat.com>
Date: Fri, 31 May 2019 18:18:17 +0200

> On Fri, 31 May 2019 08:51:43 +0200 Tom Barbette <barbette@....se> wrote:
> 
>> I wonder if it doesn't simply come from mlx5/en_main.c:
>> rq->buff.map_dir = rq->xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;
>> 
> 
> Nope, that is not the problem.

And it's easy to test this theory by forcing DMA_FROM_DEVICE.