Daniel, There was an earlier post that jiffies can be changed I have read the earlier too, never tried. I have also read that the impact is the interrupt handler and respective tasklets based on timer, etc start running more frequently thereby affecting the overall system performance. There are processor and platform specific ways of getting more finer timer information including registers like the TSC(time stamp counter) udelay, etc are typically implemented using tight loops or platform specific manner. For ppc, there is a ppc asm instruction and alternative in __const_udelay() and udelay() in include/asm-ppc/delay.h for i386, check the TSC and asm implementation called from __delay() in arch/i386/lib/delay.c Needless to say neither are approximations! :) Another project worth a look is High Res POSIX timers http://sourceforge.net/projects/high-res-timers/ The readme of the project is also a good intro http://sourceforge.net/project/shownotes.php?group_id=20460&release_id=46217 Finally, it would help to read the timer chapter, "Flow of time" in the linux device drivers, ed 2 book at http://www.xml.com/ldd/chapter/book/ch06.html or even better buy that book, it is worth it. Regards Amit Daniel Marian wrote: > Hello Amit/All, > If the timer granularity cannot go below 10ms then how is the functionality of the nanosleep and usleep > system calls in Linux implemented ? > > Is it an approximate ? > How do I know the clock ticks in a Linux box(i386) > Like /proc/cpuinfo etc. > > Is the timer granularity in the kernel different? > > I feel all the above are newbie questions sorry abt it > > TIA > kind regards, > daniel marian. > > >>Daniel, >> >>It probably won't work, that is the timeout will occur only at 10ms, >>that is per tick(timer interrupt) >> >>Amit >> >> >>Daniel Marian wrote: >> >>>Hello, >>> The tick in Linux is 10ms. >>>In my userspace program can I have a timeout value less than this granularity. >>> >>>Example a timeout value of 4 milliseconds. >>>If this is possible, how is this taken care by the kernel ? >>> >>>thanks, >>>daniel. >> >> >> > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
