linux-kernel - Re: [PATCHv7 18/33] lib/vdso: Add unlikely() hint into vdso_read

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Message-ID: <c749983f-24a8-a159-5e29-6fdd741f6023@arm.com>
Date:   Thu, 24 Oct 2019 14:14:19 +0100
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Andrei Vagin <avagin@...il.com>
Cc:     Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org,
        Dmitry Safonov <0x7f454c46@...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>,
        Thomas Gleixner <tglx@...utronix.de>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCHv7 18/33] lib/vdso: Add unlikely() hint into
 vdso_read_begin()

Hi Andrei,

On 10/24/19 10:30 AM, Vincenzo Frascino wrote:
[...]
>> Here is my test:
>> https://github.com/avagin/vdso-perf
>>
>> It is calling clock_gettime() in a loop for three seconds and then
>> reports a number of iterations.
>>
> 
> I am happy to run the test on arm64 and provide some results.
>

Please find below the results:

clock            | before     | after      | diff
==================================================
monotonic          17326692     17951770     3.6%
monotonic-coarse   43624027     44215292     1.3%
monotonic-raw      17541809     17554932     0.1%
boottime           17334982     17954361     3.5%

The improvement for arm64 for monotonic and boottime is around 3.5%.

I created a pull request on github to send to you back the changes I had
to do to vdso-perf to cross-compile it on arm64 [1].

[1] https://github.com/avagin/vdso-perf/pull/1


>> Thanks,
>> Andrei
>>
> 

-- 
Regards,
Vincenzo