On Mon, Aug 23, 2010 at 01:41:13PM -0700, john stultz wrote: > As I mentioned in the previous mail, I agree the new functionality > (adjusting the time by an offset instantaneously) is useful, but I'd > prefer it be done initially within the existing adjtimex() interface. But the adjtimex does not support nanosecond resolution. > Then if the posix-time clock_id multiplexing version of adjtimex is > found to be necessary, the new syscall should be introduced, using the > same API (not all clock_ids need to support all the adjtimex modes, but > the new interface should be sufficient for NTPd to use). Would the new syscall need to take a struct timex? If so, I think it not worth the effort of adding a syscall. Instead, we can just add "clockid" flags into the mode field. > There are some other conceptual issues this new syscall introduces: > > 1) While clock_adjtimex(CLOCK_REALTIME,...) would be equivalent to > adjtimex(), would clock_adjtimex(CLOCK_MONOTONIC,...) make sense? > > Given CLOCK_MONOTONIC and CLOCK_REALTIME are both based off the same > notion of time, but offset from each other, any adjustment to one clock > would be reflected in the other. However, the API would make it seem > like they could be adjusted independently. You could adjust the frequency of either one. As a side effect, the other clock would also be adjusted. You can only change the time offset on CLOCK_REALTIME, and that would have no effect on CLOCK_MONOTONIC. > 2) The same issue in #1 exists for CLOCK_REALTIME/MONOTONIC_COARSE > variants. > > 3) Freq steering for MONOTONIC_RAW would defeat the purpose of the > clock_id. If I understand correctly, MONOTONIC_RAW is just access to the hardware counter? > 4) Does adjustments to CPU_TIME clock_ids make sense? Don't think so. Thanks, Richard -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html