ah, I just figured out why I thought that tsleep() had to
run at splstatlclock():   it calls mi_switch(), and the comment
right before mi_switch sez:

/*
 * The machine independent parts of mi_switch().
 * Must be called at splstatclock() or higher.
 */

-Chuck


I wrote:
> the issue isn't that statclock() is slow, the issue is that tsleep()
> is slow and having it run at splhigh() is bad.  hmm, perhaps I've
> been mistaken about the whole statclock() thing... for some reason
> I've been thinking that changing the splhigh()s in tsleep() to
> splstatclock() was the right thing to do, but looking at it again,
> I don't know why I think that anymore.  it seems like having statclock()
> run in the middle of tsleep() would be fine.
> 
> let me go try making an splwakeup() and see if that does the trick.
> 
> -Chuck