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

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Message-ID: <20251226115848.298465d4@gandalf.local.home>
Date: Fri, 26 Dec 2025 11:58:48 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: "Yury Norov (NVIDIA)" <yury.norov@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Christophe Leroy
 <chleroy@...nel.org>, 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>, Rodrigo Vivi <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, intel-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-modules@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/7] kernel.h: drop trace_printk.h

On Thu, 25 Dec 2025 12:09:29 -0500
"Yury Norov (NVIDIA)" <yury.norov@...il.com> wrote:

> The trace_printk.h header is debugging-only by nature, but now it's
> included by almost every compilation unit via kernel.h.
> 
> Removing trace_printk.h saves 1.5-2% of compilation time on my
> Ubuntu-derived x86_64/localyesconfig.
> 
> There's ~30 files in the codebase, requiring trace_printk.h for
> non-debugging reasons: mostly to disable tracing on panic or under
> similar conditions. Include the header for those explicitly.
> 
> This implicitly decouples linux/kernel.h and linux/instruction_pointer.h
> as well, because it has been isolated to trace_printk.h early in the
> series.
> 
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>

I'm still against this patch. It means every time someone adds
trace_printk() they need to add the header for it.

trace_printk() should be as available to the kernel as printk() is. If
there's a place that one can add printk() without adding a header, then
they should be able to add trace_printk() to that same location without
adding any header. If that's not the case, then I'm adding an official

 Nacked-by: Steven Rostedt <rostedt@...dmis.org>

I'm fine for trying other ways to speed up the compilation, but removing
full access to trace_printk() isn't one of them.

-- Steve