Re: [Xen-devel] [PATCH 0/2] range timer support

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 28/10/08 06:57, "Yu, Ke" <ke.yu@xxxxxxxxx> wrote:

> - Per Keir's comment, more usage is found: use the range timer in HVM virtual
> periodic timer (xen/arch/x86/hvm/vpt.c). Since vpt has the logic to handle
> missing ticks, it is an ideal place to use range timer.

The fact is that just about any timer in Xen could be much sloppier than it
is. What about if we just make slop configurable and change the default up
to say 1ms? Then for lower power you could bump it some more at the cost of
things like scheduling getting a bit less accurate (and frankly does that
matter? :-). My fear with range timers is that it'll actually creep out to
nearly all current users of the timer interface, and they'll all need to
express some slightly suspect policy about how much inaccuracy they can cope
with. Fact is, in just about all cases, that's not an obvious thing to be
able to specify. In fact it's a tradeoff -- e.g., between power consumption
and 'accuracy' -- which is perhaps better centrally managed and why I think
some centrally tweakable knob like the existing SLOP macro may actually be a
better thing to work with.

 -- Keir



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