linux-kernel - Re: [PATCH] compiler_types: Introduce inline_for

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Message-Id: <20260118160125.82f645575f8327651be95070@linux-foundation.org>
Date: Sun, 18 Jan 2026 16:01:25 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Laight <david.laight.linux@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>, linux-kernel
 <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org, Jakub Kicinski
 <kuba@...nel.org>, Eric Dumazet <eric.dumazet@...il.com>, Paolo Abeni
 <pabeni@...hat.com>, Nicolas Pitre <npitre@...libre.com>
Subject: Re: [PATCH] compiler_types: Introduce inline_for_performance

On Sun, 18 Jan 2026 22:58:02 +0000 David Laight <david.laight.linux@...il.com> wrote:

> > mm/ alone has 74 __always_inlines, none are documented, I don't know
> > why they're present, many are probably wrong.
> > 
> > Shit, uninlining only __get_user_pages_locked does this:
> > 
> >    text	   data	    bss	    dec	    hex	filename
> >  115703	  14018	     64	 129785	  1faf9	mm/gup.o
> >  103866	  13058	     64	 116988	  1c8fc	mm/gup.o-after
> 
> The next questions are does anything actually run faster (either way),
> and should anything at all be marked 'inline' rather than 'always_inline'.
> 
> After all, if you call a function twice (not in a loop) you may
> want a real function in order to avoid I-cache misses.

yup

> But I'm sure there is a lot of code that is 'inline_for_bloat' :-)

ooh, can we please have that?


I do think that every always_inline should be justified and commented,
but I haven't been energetic about asking for that.

A fun little project would be go through each one, figure out whether
were good reasons and if not, just remove them and see if anyone
explains why that was incorrect.