[lkml]   [2005]   [Jul]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH] i386: Selectable Frequency of the Timer Interrupt
    On Thu, Jul 14, 2005 at 12:25:40PM +0200, Krzysztof Halasa wrote:
    > Linus Torvalds <> writes:
    > > And in short-term things, the timeval/jiffie conversion is likely to be a
    > > _bigger_ issue than the crystal frequency conversion.
    > >
    > > So we should aim for a HZ value that makes it easy to convert to and from
    > > the standard user-space interface formats. 100Hz, 250Hz and 1000Hz are all
    > > good values for that reason. 864 is not.
    > Probably only theoretical, and probably the hardware isn't up to it...
    > But what if we have:
    > - 64-bit jiffies done in hardware (a counter). 1 cycle = 1 microsecond
    > or even a CPU clock cycle. Can *APIC or another HPET do that?

    HPETs have a fixed frequency (usually 14.31818 MHz, but that depends
    on the manufacturer).

    > - 64-bit "match timer" (i.e., a register in the counter which fires IRQ
    > when it matches the counter value)

    That's implemented in the HPET hardware.

    > - the CPU(s) sorting the timer list and programming "match timer" with
    > software timer next to be executed. Upon firing the timer, a new "next
    > to be executed" timer would be programmed into the counter's "match
    > timer".
    > We would have no timer ticks when nobody requested them - the CPUs would
    > be allowed to sleep for, say, even 50 ms when no task is RUNNING.

    Vojtech Pavlik
    SuSE Labs, SuSE CR
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-07-14 14:23    [W:0.021 / U:17.756 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site