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

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Message-ID: <878smfa66i.fsf@nanos.tec.linutronix.de>
Date:   Fri, 10 Jan 2020 12:42:45 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...il.com>,
        Adrian Reber <adrian@...as.de>,
        Andrei Vagin <avagin@...nvz.org>,
        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>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCHv8 02/34] lib/vdso: make do_hres and do_coarse as __always_inline

Vincenzo Frascino <vincenzo.frascino@....com> writes:
> On 11/12/19 1:26 AM, Dmitry Safonov wrote:
>> +» » vd·=·&vd[CS_HRES_COARSE];
>> +out_hres:
>> +» » return·do_hres(vd,·clock,·ts);
>> » }·else·if·(msk·&·VDSO_COARSE)·{
>> » » do_coarse(&vd[CS_HRES_COARSE],·clock,·ts);
>> » » return·0;
>> » }·else·if·(msk·&·VDSO_RAW)·{
>> -» » return·do_hres(&vd[CS_RAW],·clock,·ts);
>> +» » vd·=·&vd[CS_RAW];
>> +» » /*·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.

Thanks,

        tglx