netdev - Re: [PATCH net-next] net: stmmac: Fix page pool size

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Date:   Mon, 23 Sep 2019 12:00:31 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Bitan Biswas <bbiswas@...dia.com>, netdev@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH net-next] net: stmmac: Fix page pool size

On Mon, Sep 23, 2019 at 11:59:15AM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> The size of individual pages in the page pool in given by an order. The
> order is the binary logarithm of the number of pages that make up one of
> the pages in the pool. However, the driver currently passes the number
> of pages rather than the order, so it ends up wasting quite a bit of
> memory.
> 
> Fix this by taking the binary logarithm and passing that in the order
> field.
> 
> Fixes: 2af6106ae949 ("net: stmmac: Introducing support for Page Pool")
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

I fumbled the git format-patch incantation. This should've been marked
v2.

Thierry

> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index ecd461207dbc..f8c90dba6db8 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1550,13 +1550,15 @@ static int alloc_dma_rx_desc_resources(struct stmmac_priv *priv)
>  	for (queue = 0; queue < rx_count; queue++) {
>  		struct stmmac_rx_queue *rx_q = &priv->rx_queue[queue];
>  		struct page_pool_params pp_params = { 0 };
> +		unsigned int num_pages;
>  
>  		rx_q->queue_index = queue;
>  		rx_q->priv_data = priv;
>  
>  		pp_params.flags = PP_FLAG_DMA_MAP;
>  		pp_params.pool_size = DMA_RX_SIZE;
> -		pp_params.order = DIV_ROUND_UP(priv->dma_buf_sz, PAGE_SIZE);
> +		num_pages = DIV_ROUND_UP(priv->dma_buf_sz, PAGE_SIZE);
> +		pp_params.order = ilog2(num_pages);
>  		pp_params.nid = dev_to_node(priv->device);
>  		pp_params.dev = priv->device;
>  		pp_params.dma_dir = DMA_FROM_DEVICE;
> -- 
> 2.23.0
> 

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