Messages in this thread | | | Subject | Re: Sub jiffy delay? | From | Steven Rostedt <> | Date | Wed, 23 Nov 2005 16:20:42 -0500 |
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On Wed, 2005-11-23 at 15:39 -0500, Rick Niles wrote: > I need to service a piece of hardware about every 400-500 > microseconds, but I really don't want to change the value of HZ, which > in my version of the 2.6 kernel is 1000. The hardware doesn't have an > interrupt so the nasty hack I've been doing is to service the hardware > repeatedly in a loop for about 600 microseconds by watching the > do_gettimeofday(), set a timer for the next jiffy and repeat. This leaves less than 400 microseconds / millisecond for the kernel and anything else on the system to run. > > Obviously, this sucks, but it does work. I am working with the > hardware guy to add an interrupt to the hardware. However, I don't > want every user of the hardware without the interrupt to have to > rebuild the kernel with a different value of HZ. So does anyone have > any better ideas on what I can do?
Have you looked at Thomas Gleixner's ktimer/HRT patches. It gives you a way to set a timer to go off within a jiffy.
http://tglx.de/ktimers.html
-- Steve
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