linux-kernel - Re: [PATCH 2/4] dev_printk: Add and use dev_no

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Date: Wed, 28 Feb 2024 20:33:19 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Chris Down <chris@...isdown.name>, Petr Mladek <pmladek@...e.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jessica Yu <jeyu@...nel.org>, 
	Steven Rostedt <rostedt@...dmis.org>, John Ogness <john.ogness@...utronix.de>, 
	Sergey Senozhatsky <senozhatsky@...omium.org>, Jason Baron <jbaron@...mai.com>, 
	Jim Cromie <jim.cromie@...il.com>, Ilya Dryomov <idryomov@...il.com>, Xiubo Li <xiubli@...hat.com>, 
	Jeff Layton <jlayton@...nel.org>, linux-kernel@...r.kernel.org, 
	ceph-devel@...r.kernel.org
Subject: Re: [PATCH 2/4] dev_printk: Add and use dev_no_printk()

Hi Andy,

On Wed, Feb 28, 2024 at 6:39 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> On Wed, Feb 28, 2024 at 03:00:03PM +0100, Geert Uytterhoeven wrote:
> > When printk-indexing is enabled, each dev_printk() invocation emits a
> > pi_entry structure.  This is even true when the dev_printk() is
> > protected by an always-false check, as is typically the case for debug
> > messages: while the actual code to print the message is optimized out by
> > the compiler, the pi_entry structure is still emitted.
> >
> > Avoid emitting pi_entry structures for unavailable dev_printk() kernel
> > messages by:
> >   1. Introducing a dev_no_printk() helper, mimicked after the existing
> >      no_printk() helper, which calls _dev_printk() instead of
> >      dev_printk(),
> >   2. Replacing all "if (0) dev_printk(...)" constructs by calls to the
> >      new helper.
> >
> > This reduces the size of an arm64 defconfig kernel with
> > CONFIG_PRINTK_INDEX=y by 957 KiB.
>
> ...
>
> > +/*
> > + * Dummy dev_printk for disabled debugging statements to use whilst maintaining
>
> dev_printk()

I fully agree.  But the surrounding comments don't, so I gave in.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds