netdev - Re: [PATCH net-next 1/6] r8169: change driver data type

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Message-ID: <ccf8a37b-203c-8b54-958e-757d3e9088e5@gmail.com>
Date:   Sun, 31 May 2020 09:57:01 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 1/6] r8169: change driver data type

On 31.05.2020 07:17, Stephen Hemminger wrote:
> On Sat, 30 May 2020 23:54:36 +0200
> Heiner Kallweit <hkallweit1@...il.com> wrote:
> 
>> Change driver private data type to struct rtl8169_private * to avoid
>> some overhead.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
>> ---
> 
> Are you sure about this. Using netdev_priv() is actually at a fixed
> offset from netdev, and almost always the compiler can optimize and
> use one register.  Look at the assembly code difference of what you
> did.
> 
When saying overhead I had the source code in mind. With regard to
the generated code you're right, however no hot path is touched here.