netdev - Re: [PATCH net-next 4/8] net/mlx4_en: Add __GFP_COLD gfp flags in alloc

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Date:	Thu, 30 Oct 2014 10:15:33 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Or Gerlitz <ogerlitz@...lanox.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Matan Barak <matanb@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>,
	Saeed Mahameed <saeedm@...lanox.com>,
	Shani Michaeli <shanim@...lanox.com>,
	Ido Shamay <idos@...lanox.com>
Subject: Re: [PATCH net-next 4/8] net/mlx4_en: Add __GFP_COLD gfp flags in
 alloc_pages

On Thu, 2014-10-30 at 18:06 +0200, Or Gerlitz wrote:
> From: Ido Shamay <idos@...lanox.com>
> 
> Needed in order to get cache cold pages (L3 flushed) for HW scatter.
> 
> Otherwise memory may flush those entries when the packet comes from
> PCI, causing back pressure resulting in BW decrease.
> 
> Signed-off-by: Ido Shamay <idos@...lanox.com>
> Signed-off-by: Amir Vadai <amirv@...lanox.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 4cb716f..9d616a8 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -54,7 +54,7 @@ static int mlx4_alloc_pages(struct mlx4_en_priv *priv,
>  	dma_addr_t dma;
>  
>  	for (order = MLX4_EN_ALLOC_PREFER_ORDER; ;) {
> -		gfp_t gfp = _gfp;
> +		gfp_t gfp = _gfp | __GFP_COLD;

This should be set by callers, to avoid extra code

GFP_ATOMIC | __GFP_COLD

or

GFP_KERNEL | __GFP_COLD

>  
>  		if (order)
>  			gfp |= __GFP_COMP | __GFP_NOWARN;


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