linux-kernel - Re: [PATCH v4 7/7] kernel.h: drop trace

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Message-ID: <63a00906-a5c6-43de-82ce-328c8eaa7d3f@kernel.org>
Date: Mon, 5 Jan 2026 19:21:20 +0100
From: "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>
To: Joel Fernandes <joelagnelf@...dia.com>,
 Steven Rostedt <rostedt@...dmis.org>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Yury Norov <yury.norov@...il.com>, Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Randy Dunlap <rdunlap@...radead.org>, Ingo Molnar <mingo@...nel.org>,
 Jani Nikula <jani.nikula@...ux.intel.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 David Laight <david.laight@...box.com>, Petr Pavlu <petr.pavlu@...e.com>,
 Andi Shyti <andi.shyti@...nel.org>, Vivi Rodrigo <rodrigo.vivi@...el.com>,
 Tvrtko Ursulin <tursulin@...ulin.net>, Daniel Gomez <da.gomez@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
 "linux-trace-kernel@...r.kernel.org" <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 7/7] kernel.h: drop trace_printk.h

Le 05/01/2026 à 18:11, Joel Fernandes a écrit :
> 
> 
> On 1/5/2026 11:39 AM, Steven Rostedt wrote:
>> On Sun, 4 Jan 2026 02:20:55 +0200
>> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
>>
>>>>
>>>> I do not think it is necessary to move it.
>>>
>>> I'm not talking about move, I'm talking about the C 101 thingy. Any custom API
>>> should be included before use, otherwise compiler won't see it. Which header do
>>> you want to include to have this API being provided? Note, it's really bad
>>> situation right now with the header to be included implicitly via non-obvious
>>> or obscure path. The discussion moved as far as I see it towards the finding a
>>> good place for the trace_printk.h.
>>
>> It's not a normal API. It's for debugging the kernel. Thus it should be
>> available everywhere without having to add a header. Hence, the best place
>> to include trace_printk.h, is in kernel.h.
>>
>> I'm thinking that my proposed config option is the best solution now. For
>> those that do not care about debugging the kernel, you enable the
>> "HIDE_TRACE_PRINTK" config so that your builds will be "quicker". But for
>> everyone else, it will not slow down their workflow when they need to debug
>> code.
> 
> 100% agree. We do have people running custom configs for faster builds, so this
> hide thing could be enabled there assuming those don't care about debug.
> 
> In other words, "If it aint broke, don't fix it".

But if I understand correctly, it would save 2% build time. That means 
12 secondes on a 10 minutes build. Is it really worth it ?

Christophe