linux-kernel - Re: [PATCH net-next] net: generalize calculation of skb extensions length

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Message-ID: <1e1dde74-edc6-4306-9b1b-0a1b5a658b67@weissschuh.net>
Date:   Wed, 23 Aug 2023 10:14:48 +0200 (GMT+02:00)
From:   linux@...ssschuh.net
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Thomas Weißschuh <linux@...ssschuh.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Robert Marko <robimarko@...il.com>
Subject: Re: [PATCH net-next] net: generalize calculation of skb extensions
 length

Hi Jakub,


Aug 23, 2023 03:46:48 Jakub Kicinski <kuba@...nel.org>:

> On Tue, 22 Aug 2023 08:51:57 +0200 Thomas Weißschuh wrote:
>> Remove the necessity to modify skb_ext_total_length() when new extension
>> types are added.
>> Also reduces the line count a bit.
>>
>> With optimizations enabled the function is folded down to a constant
>> value as before.
>
> Could you include more info about the compiler versions you tried
> and maybe some objdump? We'll have to take your word for it getting
> optimized out, would be great if we had more proof in the commit msg.
> --
> pw-bot: cr

Thanks for the feedback.
I'll send a v2 with more background soon.

On the other hand this function is only ever
executed once, so even if it is slightly inefficient
it shouldn't matter.

Thomas