On 2018-10-27, 12:55, "fio-owner@vger.kernel.org on behalf of Jens Axboe" <fio-owner@vger.kernel.org on behalf of axboe@kernel.dk> wrote:

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    On 10/26/18 6:54 AM, Mohanraj B wrote:
    > Hello,
    >
    > I am trying to check how option --clocksource works.
    >
    >
    > bash# fio --name job1 --size 10m --clocksource 2
    >         valid values: gettimeofday Use gettimeofday(2) for timing
    >                     : clock_gettime Use clock_gettime(2) for timing
    >                     : cpu        Use CPU private clock
    >
    > fio: failed parsing clocksource=2
    >
    > bash# fio --name job1 --size 10m --clocksource gettimeofday(2)
    > bash: syntax error near unexpected token `('
    >
    > Below command works fine.
    > bash# fio --name job1 --size 10m --clocksource gettimeofday
    >
    > It runs without error but quiet not sure how to see the effect of this
    > option. also tried other options - clock_gettime, cpu gettimeofday and
    > dont see any difference.
    >
    > Also is there any error in documentation passing gettimeofday(2)
    > throws parse error.

    The format is 'value' 'help', so you'd want to do:

    --clocksource=gettimeofday

    for instance.

    --
    Jens Axboe

Hello, Mohanraj

The help output that you see above states that using --clocksource=gettimeofday will use the gettimeofday function as defined in the man page in the section (2), which is where all the system calls manuals are stored.  The (2) is  not meant to be part of the command line, it is part of the description of the help text, which tells you where to find more information on what is being used to implement the clocksource.

Hope that helps clarify the help text.

Regards,
Mark