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

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Message-ID: <aU_xG7pK9iauff65@smile.fi.intel.com>
Date: Sat, 27 Dec 2025 16:45:47 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: "Yury Norov (NVIDIA)" <yury.norov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.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, Dec 26, 2025 at 11:58:48AM -0500, Steven Rostedt 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. 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.

I interpreted this as if the header inclusion should be moved from kernel.h
to printk.h as a compromise that satisfies all (?) stakeholders. Is it possible
approach?

-- 
With Best Regards,
Andy Shevchenko