RE: [Xen-devel] [PATCH] Yield to VCPU hcall, spinlock yielding
"Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
wrote on 06/08/2005 05:29:21 PM:
> We might be able to come up with a cheaper hack for doing this. The
> notifaction scheme is already on the expensive side, and adding two
> extra passes through the scheduler could totally doom it.
I agree that whether we can tolerate
the cost of preemption notification interrupts is still very much an open
question. I doubt that the additional costs of unblocking and blocking
a kernel thread will be decisive.
I don't view the high-priority kernel
thread idea as a "hack". In conjunction with CONFIG_PREEMPT,
it is a straight-forward solution to a real problem: From the notification
interrupt handler, how do you get the kernel to yield as quickly as possible
but only at such time as no kernel locks are held? A newly-unblocked
high-priority thread will run at exactly the right time, with no new hacking
on Linux locking or scheduling code.
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