netdev - Re: [PATCH RFC] net/mlx5_en: switch to Toeplitz RSS hash by default

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Date:   Sun, 2 Sep 2018 12:29:25 +0300
From:   Tariq Toukan <tariqt@...lanox.com>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        netdev@...r.kernel.org, Saeed Mahameed <saeedm@...lanox.com>,
        Gal Pressman <galp@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [PATCH RFC] net/mlx5_en: switch to Toeplitz RSS hash by default



On 31/08/2018 2:29 PM, Konstantin Khlebnikov wrote:
> XOR (MLX5_RX_HASH_FN_INVERTED_XOR8) gives only 8 bits.
> It seems not enough for RFS. All other drivers use toeplitz.
> 
> Driver mlx4_en uses Toeplitz by default and warns if hash XOR is used
> together with NETIF_F_RXHASH (enabled by default too): "Enabling both
> XOR Hash function and RX Hashing can limit RPS functionality".
> 
> XOR is default in mlx5_en since commit 2be6967cdbc9
> ("net/mlx5e: Support ETH_RSS_HASH_XOR").
> 
> Hash function could be set via ethtool. But it would be nice to have
> single standard for drivers or proper description why this one is special.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> ---

Hi Konstantin,

Thanks for the patch.

I understand the motivation.

This change affects the default out-of-the-box behavior and requires a 
full performance cycle. We'll run performance regression tomorrow, 
results should be ready by EOW.

I'll update.

Regards,
Tariq