netdev - Re: [PATCH 3/3] net: fs_enet: make rx

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Message-ID: <d0c26b9f-2a35-5e98-5d1d-06c649e02827@gmail.com>
Date:   Wed, 24 Aug 2016 10:14:16 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Pantelis Antoniou <pantelis.antoniou@...il.com>,
        Vitaly Bordug <vbordug@...mvista.com>, davem@...emloft.net
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 3/3] net: fs_enet: make rx_copybreak value configurable

On 08/24/2016 03:36 AM, Christophe Leroy wrote:
> Measurement shows that on a MPC8xx running at 132MHz, the optimal
> limit is 112:
> * 114 bytes packets are processed in 147 TB ticks with higher copybreak
> * 114 bytes packets are processed in 148 TB ticks with lower copybreak
> * 128 bytes packets are processed in 154 TB ticks with higher copybreak
> * 128 bytes packets are processed in 148 TB ticks with lower copybreak
> * 238 bytes packets are processed in 172 TB ticks with higher copybreak
> * 238 bytes packets are processed in 148 TB ticks with lower copybreak
> 
> However it might be different on other processors
> and/or frequencies. So it is useful to make it configurable.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>  drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c | 8 +++++---
>  include/linux/fs_enet_pd.h                            | 1 -
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
> index addcae6..b59bbf8 100644
> --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
> +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
> @@ -60,6 +60,10 @@ module_param(fs_enet_debug, int, 0);
>  MODULE_PARM_DESC(fs_enet_debug,
>  		 "Freescale bitmapped debugging message enable value");
>  
> +static int rx_copybreak = 240;
> +module_param(rx_copybreak, int, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(rx_copybreak, "Receive copy threshold");

There is an ethtool tunable knob for copybreak now, which you should
prefer over a module parameter, see
drivers/net/ethernet/cisco/enic/enic_ethtool.c
-- 
Florian