On Tue, Jun 10, 2008 at 5:39 PM, Stephane Chazelas <[EMAIL PROTECTED]> wrote: > Package: manpages-dev > Version: 2.79-4 > Severity: wishlist > > > The BUGS section in nanosleep(2) gives: > > BUGS > The current implementation of nanosleep() is based on the > normal kernel timer mechanism, which has a resolution of > 1/HZ s (see time(7)). Therefore, nanosleep() pauses > always for at least the specified time, however it can > take up to 10 ms longer than specified until the process > becomes runnable again. For the same reason, the value > returned in case of a delivered signal in *rem is usually > rounded to the next larger multiple of 1/HZ s. > > Old behavior > In order to support applications requiring much more > precise pauses (e.g., in order to control some > time-critical hardware), nanosleep() would handle pauses > of up to 2 ms by busy waiting with microsecond > precision when called from a process scheduled under a > real-time policy like SCHED_FIFO or SCHED_RR. This > special extension was removed in kernel 2.5.39, hence is > still present in current 2.4 kernels, but not in 2.6 > kernels. > > In Linux 2.4, if nanosleep() is stopped by a signal > (e.g., SIGTSTP), then the call fails with the error EINTR > after the process is resumed by a SIGCONT signal. If > the system call is subsequently restarted, then the time > that the process spent in the stopped state is not > counted against the sleep interval. > > > I think it should be worth mentionning that since 2.6.16, on > some architectures, the kernel can be configured with high > resolution timers which makes nanosleep(2) a lot more accurate > and voids the first comment above.
Stephane Thanks for your note. Can you provide some further details -- for example, can you tell me any of the following: which architectures? what config options are required? what determines the accuracy that can be achieved with HR timers? Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
