On Fri, 2008-01-25 at 15:07 +0100, Roman Zippel wrote: > Hi, > > On Wed, 23 Jan 2008, john stultz wrote: > > > This difference in calculation was causing the clocksource correction > > code to apply a correction factor to the clocksource so the two > > intervals were the same, however this results in the actual frequency of > > the clocksource to be made incorrect. I believe this difference would > > affect all clocksources, although to differing degrees depending on the > > clocksource resolution. > > Let's look at why the correction is done in first place. The update steps > don't add up precisely to 1sec (LATCH*HZ != CLOCK_TICK_RATE), so a small > addjustment is used to make up for it. The problem here is that if the > update frequency changes, the addjustment isn't correct anymore. > The simple fix is to just omit the addjustment in these cases in ntp.c: > > #if NTP_INTERVAL_FREQ == HZ > ... > #else > #define CLOCK_TICK_ADJUST 0 > #endif
Hmmm, although this doesn't explain why the issue is seen when NTP_INTERVAL_FREQ == HZ (as it is in my system's case). Or am I missing something? Regardless, current_tick_length() really is the base interval we're using in the error accumulation loop, so it seems the cleanest interface to use (just to avoid redundancy at least) when establishing the clocksource's interval length. Or do you not agree? thanks -john -- 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/
