netdev - Re: [PATCH] amd-xgbe: use PAGE_ALLOC_COSTLY_ORDER in xgbe_map_rx

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Date:   Fri, 2 Jun 2017 15:52:16 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] amd-xgbe: use PAGE_ALLOC_COSTLY_ORDER in
 xgbe_map_rx_buffer

On 6/2/2017 10:54 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> xgbe_map_rx_buffer is rather confused about what PAGE_ALLOC_COSTLY_ORDER
> means. It uses PAGE_ALLOC_COSTLY_ORDER-1 assuming that
> PAGE_ALLOC_COSTLY_ORDER is the first costly order which is not the case
> actually because orders larger than that are costly. And even that
> applies only to sleeping allocations which is not the case here. We
> simply do not perform any costly operations like reclaim or compaction
> for those. Simplify the code by dropping the order calculation and use
> PAGE_ALLOC_COSTLY_ORDER directly.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>   drivers/net/ethernet/amd/xgbe/xgbe-desc.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-desc.c b/drivers/net/ethernet/amd/xgbe/xgbe-desc.c
> index b3bc87fe3764..0a98c369df20 100644
> --- a/drivers/net/ethernet/amd/xgbe/xgbe-desc.c
> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-desc.c
> @@ -324,7 +324,7 @@ static int xgbe_map_rx_buffer(struct xgbe_prv_data *pdata,
>   			      struct xgbe_ring *ring,
>   			      struct xgbe_ring_data *rdata)
>   {
> -	int order, ret;
> +	int ret;
>   
>   	if (!ring->rx_hdr_pa.pages) {
>   		ret = xgbe_alloc_pages(pdata, &ring->rx_hdr_pa, GFP_ATOMIC, 0);
> @@ -333,9 +333,8 @@ static int xgbe_map_rx_buffer(struct xgbe_prv_data *pdata,
>   	}
>   
>   	if (!ring->rx_buf_pa.pages) {
> -		order = max_t(int, PAGE_ALLOC_COSTLY_ORDER - 1, 0);
>   		ret = xgbe_alloc_pages(pdata, &ring->rx_buf_pa, GFP_ATOMIC,
> -				       order);
> +				       PAGE_ALLOC_COSTLY_ORDER);
>   		if (ret)
>   			return ret;
>   	}
>