On 09/25/2009 11:43 PM, Joerg Roedel wrote:
On Wed, Sep 23, 2009 at 05:09:38PM +0300, Avi Kivity wrote:
We haven't sorted out what is the correct thing to do here. I think we
should go for a directed yield, but until we have it, you can use
hrtimers to sleep for 100 microseconds and hope the holding vcpu will
get scheduled. Even if it doesn't, we're only wasting a few percent cpu
time instead of spinning.
How do you plan to find out to which vcpu thread the current thread
should yield?
We can't find exactly which vcpu, but we can:
- rule out threads that are not vcpus for this guest
- rule out threads that are already running
A major problem with sleep() is that it effectively reduces the vm
priority relative to guests that don't have spinlock contention. By
selecting a random nonrunnable vcpu belonging to this guest, we at least
preserve the guest's timeslice.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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