Re: FreeBSD/Xen ugliness

[Kip Macy <kmacy@fsmware.com>]

I've seen the same timing issues. We do call yield where appropriate:

static void
cpu_idle_default(void)
{
#if 0
        /*
         * we must absolutely guarentee that hlt is the
         * absolute next instruction after sti or we
         * introduce a timing window.
         */
        __asm __volatile("sti; hlt");
#endif
        enable_intr();
        HYPERVISOR_yield();
}


So I'm not sure what the problem is. After the 5.3 work and coredump is
done I might look into it. There may have been some fixes to the clock
code in the meantime.


				-Kip


On Sat, 8 Jan 2005, Derrik Pates wrote:

> Kip:
>
> Well, I have good news; thanks to Darren Tucker pointing out that the
> boot.netif.* parameters _have_ to be added, I was able to successfully
> boot your FreeBSD/Xen kernel. It seems to work okay so far. It fairly
> regularly (every few minutes or so) spits out a line like:
>
> Expensive timeout(9) function: 0xc00b0bd0(0) 0.010000854 s
>
> at me, but it seems to otherwise behave as FreeBSD should. The only
> thing I've noticed so far is that, looking at the output of 'xm list',
> its domain's virtual-time clock seems to grow at a constant rate. I'm
> guessing this means it doesn't call up to the hypervisor and say "Please
> schedule someone else, I'm idle right now" when it has nothing to do. It
> doesn't seem to affect the performance of other domains though, but I
> thought it worth pointing out. Unfortunately, I don't know enough about
> FreeBSD's scheduler to make the necessary changes to make this work as
> it should. I'll have to see about getting a proper full CVS pull of the
> sys/ tree for 5.2.1 on my FreeBSD install in VMware, and see if I can
> make a FreeBSD kernel build work; however, I'd like to see the 5.3
> kernel when you get around to it.
>
> --
> Derrik Pates
> dpates@dsdk12.net
>


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