Re: About ceph_clock_now()

["Adam C. Emerson" <aemerson@redhat.com>]

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On 25/01/2016, Willem Jan Withagen wrote:
> 1)
> Currently the code in Adam's looks like:
> #if defined(CLOCK_MONOTONIC_COARSE)
>         // Linux systems have _COARSE clocks.
>         clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
> #elif defined(CLOCK_MONOTONIC_FAST)
>         // BSD systems have _FAST clocks.
>         clock_gettime(CLOCK_MONOTONIC_FAST, &ts);
> #else
>         // And if we find neither, you may wish to consult your system's
>         // documentation.
> #warning Falling back to CLOCK_MONOTONIC, may be slow.
>         clock_gettime(CLOCK_MONOTONIC, &ts);
> #endif
> 
> And this is repeated in a few more locations.
> Moreover, it will be required to do that a few times everytime
> clock_getime is used.

I was originally thinking of just specifying the time constant, but I figured
that somehow somewhere someone might want to compile on a system without
clock_gettime. (Windows? I don't know.) Or use the fasttime library or something
where just switching out the constant wouldn't work.

I wouldn't worry about people having to do this every tie they call
clock_gettime, though, since they really ought to be going through the C++ Clock
abstraction. (At least, in the context of the Ceph codebase.)

-- 
Senior Software Engineer           Red Hat Storage, Ann Arbor, MI, US
IRC: Aemerson@{RedHat, OFTC, Freenode}
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