linux-kernel - Re: [PATCHv8 02/34] lib/vdso: make do_hres and do_coarse as __always

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Date:   Sun, 12 Jan 2020 21:27:31 -0800
From:   Andrei Vagin <avagin@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Safonov <dima@...sta.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Adrian Reber <adrian@...as.de>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jann Horn <jannh@...gle.com>, Jeff Dike <jdike@...toit.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Shuah Khan <shuah@...nel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        crml <criu@...nvz.org>, Linux API <linux-api@...r.kernel.org>,
        X86 ML <x86@...nel.org>
Subject: Re: [PATCHv8 02/34] lib/vdso: make do_hres and do_coarse as __always_inline

On Fri, Jan 10, 2020 at 4:02 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Vincenzo Frascino <vincenzo.frascino@....com> writes:
> > On 1/10/20 11:42 AM, Thomas Gleixner wrote:
> >>>> +» » /*·goto·allows·to·avoid·extra·inlining·of·do_hres.·*/
> >>>> +» » goto·out_hres;
> >>>
> >>> What is the performance impact of "goto out_hres"?
> >>
> >> On x86 it's invisible at least in my limited testing.
> >
> > On arm64 as well based on mine as well. Shall we keep the code more readable
> > here (without goto)?
>
> The delta patch below makes it readable again and also avoids the double
> inlining. Quick testing shows no difference.

My tests show no difference too and the code looks more readable. Thanks!

>
> Thanks,
>
>         tglx