linux-kernel - Re: [PATCH 0/2] generic/bitops: Always inline some more generic helpers

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Date:   Fri, 14 Jan 2022 09:12:37 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Marco Elver <elver@...gle.com>
Cc:     Borislav Petkov <bp@...en8.de>, Arnd Bergmann <arnd@...db.de>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Will Deacon <will@...nel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] generic/bitops: Always inline some more generic
 helpers

On Thu, Jan 13, 2022 at 05:58:57PM +0100, Marco Elver wrote:
> On Thu, 13 Jan 2022 at 16:53, Borislav Petkov <bp@...en8.de> wrote:
> >
> > From: Borislav Petkov <bp@...e.de>
> >
> > Hi all,
> >
> > a build report by the 0day robot:
> >
> >   https://lore.kernel.org/r/Yc7t934f%2Bf/mO8lj@zn.tnic
> >
> > made me look at asm and how gcc, at least, generates funky calls to the
> > *_bit() bit manipulation functions on x86 instead of inlining them into
> > the call sites as on x86 that's a single insn, in most of the cases.
> >
> > So PeterZ says the way to go is to always inline them. So here they are.
> > The fun thing is that on x86 there is even a size decrease of more than
> > a Kilobyte for a defconfig, which is nice, see patch 1.
> >
> > As always, comments and suggestions are welcome.
> >
> > Thx.
> >
> > Borislav Petkov (2):
> >   asm-generic/bitops: Always inline all bit manipulation helpers
> >   cpumask: Always inline helpers which use bit manipulation functions
> >
> >  include/asm-generic/bitops/instrumented-atomic.h | 12 ++++++------
> >  .../asm-generic/bitops/instrumented-non-atomic.h | 16 ++++++++--------
> >  include/linux/cpumask.h                          | 14 +++++++-------
> >  3 files changed, 21 insertions(+), 21 deletions(-)
> 
> Acked-by: Marco Elver <elver@...gle.com>
> 
> Yup, this is probably something we should have done a long time ago. :-)

Thanks, I'll go stuff it in locking/core.