linux-kernel - Re: [v3 2/3] coccinelle: api: extend memdup_user rule with vmemdup

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Message-ID: <c6809db7-2979-7057-5cac-d2d1a57e77e2@web.de>
Date:   Wed, 22 Jul 2020 08:44:29 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Julia Lawall <julia.lawall@...ia.fr>,
        Denis Efremov <efremov@...ux.com>,
        Coccinelle <cocci@...teme.lip6.fr>
Cc:     Gilles Muller <Gilles.Muller@...6.fr>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [v3 2/3] coccinelle: api: extend memdup_user rule with
 vmemdup_user()

>> Under which circumstances would you begin to care more for involved differences
>> in corresponding run time characteristics?
>
> When the difference is hours vs seconds.

Such a view can be influenced by execution environments in considerable ways.

> In this case, there are tradeoffs between the two options,

I am trying to improve the awareness for possible software design variations.

> andI don't know which would be faster,

I am curious if more contributors would get into the mood to compare
data processing approaches a bit more.

> but I think it is extremely unlikely that the difference is noticible.

But the following effects may be known for the evaluation of a SmPL rule
which was combined for two code parts.

* The SmPL dependencies are checked only once.

* Can the source code search efforts be reduced a bit?

> But if you are concerned about it, you are welcome to try.

Will anybody become interested to measure the software behaviour exactly?

Regards,
Markus