Re: TSC instead of ACPI: powerd doesn't work anymore (to be expected?)

From: David Xu (davidxu_at_freebsd.org)
Date: 10/31/05

  • Next message: David Xu: "Re: TSC instead of ACPI: powerd doesn't work anymore (to be expected?)" 
    Date: Mon, 31 Oct 2005 18:48:39 +0800
To: Poul-Henning Kamp <phk@phk.freebsd.dk>

    Poul-Henning Kamp wrote:
    > In message <4365EF7B.1020706@freebsd.org>, David Xu writes:
    >>Can we change gettimeofday and clock_gettime to lower resolution now?
    >
    >
    > I can live with gettimeofday(2) and time(3) being degraded.
    >
    > I am going to insist that clock_gettime(CLOCK_REALTIME, CLOCK_UPTIME)
    > remain precise.
    >

    In thread program, we have to use clock_gettime, for example a thread
    wants to wait for condition variable for two seconds, it has to:

    struct timespec ts;

    clock_gettime(CLOCK_REALTIME, &ts);
    ts.tv_sec += 2;
    pthread_cond_wait(&cond, &mtx);

    problem is who really cares time precise? how many people are
    really handling realtime critical tasks? this is really an
    unpleasant side effect that a simple syscall can stall cpu.

    >
    >>I think 1000hz/s is enough for most applications, since a thread can
    >>never sleep shorter than a tick for years.
    >
    >
    > (Famous last words!)
    >
    > Time is not just a matter of sleeping.
    >
    >
    >>We can introduce
    >>hrtime_t clock_gethrtime(clockid_t clock) to get hi-resolution time
    >>as the one seen in RTLinux, or gethrtime() as seen in Solaris (Daniel
    >>Eischen said?)
    >
    >
    > You know ?
    >
    > This is just a great example of why people feel the autocrap tools
    > is the way to write portable code :-(
    >
    > The open group specifically allow clock_gettime() to implement
    > more timescales, so what did those fools go and invent even more
    > library functions for ?
    >
    > Poul-Henning
    >

    You can introduce other CLOCK_..., but auto tools won't detect them too,
    this means nobody will use them except us, probably worse then
    gethrtime. :-(

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