[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Xen-devel] Question about hpet calls to set_timer

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Beth Kon <eak@xxxxxxxxxx>
  • Date: Fri, 15 Aug 2008 14:41:42 -0400
  • Delivery-date: Fri, 15 Aug 2008 13:41:12 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Hello. I'm looking over the Xen hpet.c to see what I can steal for the
qemu implementation I'm working on. (Thank you kindly :-)

One thing that doesn't make sense to me is why, in hpet_timer_fn, the
timer is set with:

set_timer(&h->timers[tn], NOW() + hpet_tick_to_ns(h, period));

rather than calculating the difference between the final value of the
comparator (after the time_after loop) and the current time. This is the
approach used in hpet_set_timer:

set_timer(&h->timers[tn], NOW() + hpet_tick_to_ns(h, diff));

and would seem to be the best way to get as close to the desired expire
time as possible. Can someone explain why the approaches are different
in these 2 places?

Elizabeth Kon (Beth)
IBM Linux Technology Center
Open Hypervisor Team
email: eak@xxxxxxxxxx

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.