Hello James, On Monday, August 11, 2008 at 16:13:50 +0100, James Youngman wrote: > To ask the obvious question, why are we doing this in userspace at > all? I'm not sure what you mean exactly. There is a principle of subsidiarity, which says that: if it can be done in userspace, then it should be done in userspace. Hwclock is probably a little bit too fat to be reasonably integrated into the kernel. This integration would pose some number of problems, as what to do with /etc/adjtime, or how to justify the necessarily very long time spent in kernel mode. The expectable benefits are quite unclear. As example, I can imagine one big improvement: The clock tick could be timestamped directly at the beginning of the RTC interrupt service routine. The benefits in terms of accuracy, low delay, and low dispersion of measures would be huge, especially on heavily loaded systems. Sounds juicy. But it doesn't require a kernelspace hwclock: The /dev/rtc device driver could be modified to do this, and pass the timestamp up to userland. An ioctl(RTC_TIMESTAMP_UIE_ON) to activate the thing, and read() would return a timeval or a timespec in addition to the usual 4 bytes. Alain. -- To unsubscribe from this list: send the line "unsubscribe util-linux-ng" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
