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

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Message-Id: <20251228133150.1d5731d04bc1b685b0fe81c1@linux-foundation.org>
Date: Sun, 28 Dec 2025 13:31:50 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: "Yury Norov (NVIDIA)" <yury.norov@...il.com>, 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 Fri, 26 Dec 2025 11:58:48 -0500 Steven Rostedt <rostedt@...dmis.org> wrote:

> 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.

um, why?  trace_printk is used 1% as often as is printk.  Seems
reasonable to include a header file to access such a rarely-used(!) and
specialized thing?