On Thu, Jul 14, 2005 at 12:25:40PM +0200, Krzysztof Halasa wrote: > Linus Torvalds <[EMAIL PROTECTED]> 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 [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
