linux-kernel - Re: [RFC/PATCH] posix-timers: make them configurable

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Date:   Fri, 9 Sep 2016 15:46:13 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Richard Cochran <richardcochran@...il.com>
cc:     John Stultz <john.stultz@...aro.org>,
        Nicolas Pitre <nico@...xnic.net>,
        Josh Triplett <josh@...htriplett.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/PATCH] posix-timers: make them configurable

On Fri, 9 Sep 2016, Richard Cochran wrote:

> On Thu, Sep 08, 2016 at 02:19:24PM -0700, John Stultz wrote:
> > Also given many other syscalls take clockids and the backing logic
> > isn't really getting removed (probably could cut the dynamic posix
> > clocks core with the same conditional), I wonder if you could get a
> > similar size win by taking a slightly more narrow cutting of the
> > subsystem. That way you could preserve the more useful clock_gettime()
> > functionality, but maybe stub out some of the less often used
> > functionality.
> 
> I want to support tinification, but I also doubt the utility of
> removing clock_gettime() and clock_nanosleep().  I can't imagine ever
> building a user space without those.  In fact, thinking about IoT,
> having good time is critical, and so these are the *last* functions I
> would remove when downsizing.

gettimeofday() gives you microsecond resolution which is good enough for
99.9% of all problems.

The only real downside is removing clock_nanosleep() because nanosleep()
does not give you the ability to schedule timers on absolute time.

Thanks,

	tglx