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

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Message-ID: <1486484783.7793.61.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 07 Feb 2017 08:26:23 -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 Tue, 2017-02-07 at 08:06 -0800, Eric Dumazet wrote:

>  		/*
>  		 * make sure we read the CQE after we read the ownership bit
>  		 */
>  		dma_rmb();
> +		prefetch(frags[0].page);

Note that I would like to instead do a prefetch(frags[1].page)

So I will probably change how ring->rx_info is allocated

wasting all that space and forcing vmalloc() is silly :

tmp = size * roundup_pow_of_two(MLX4_EN_MAX_RX_FRAGS *
                                sizeof(struct mlx4_en_rx_alloc));
ring->rx_info = vzalloc_node(tmp, node);

In most cases, using exactly 12 bytes per slot would allow better
packing. Only one cpu is using this area, no need to force strange
alignments, for the sake of avoiding a multiply !