Re: [PATCH 1/3] dynticks - implement no idle hz for x86

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Mon, Sep 05, 2005 at 01:19:28PM +0530, Srivatsa Vaddagiri wrote:
> > Despite that, the timers as implemented on the hardware are not
> > suitable for dyntick use - attempting to use them, you lose long
> > term precision of the timer interrupts.
> 
> Thats one of the problems I am seeing on x86 as well. Recovering
> wall-time precisely after sleep is tough esepcially if the interrupt
> source (PIT) and backing-time source (TSC/PM Timer/HPET) can
> drift wrt each other. PPC64 should be much better I hope (which is what I 
> intend to take up next).

This is why the config option to enable it on ARM has a warning in
there about it.  Some hardware timer implementations just aren't
suitable for this, so users should be warned about it (and are on
ARM.)

> Tony was using it to signal that all CPUs are idle and timer are
> being skipped. With the SMP changes I made, I felt it can be
> substituted with the nohz_cpu_mask bitmap and hence I removed
> it.

Well, consider that definition removed from ARM.  Forget it was even
saw it in there. 8)

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core