Gregory Haskins wrote:
Note that this is exactly what I do (though it is device specific).
venet-tap has a ioq_notifier registered on its "rx" ring (which is the
tx-ring for the guest) that simply calls ioq_notify_disable() (which
calls shm_signal_disable() under the covers) and it wakes its
rx-thread. This all happens in the context of the hypercall, which then
returns and allows the vcpu to re-enter guest mode immediately.
I think this is suboptimal. The ring is likely to be cache hot on the
current cpu, waking a thread will introduce scheduling latency + IPI
+cache-to-cache transfers.
On a benchmark setup, host resources are likely to exceed guest
requirements, so you can throw cpu at the problem and no one notices.
But I think the bits/cycle figure will decrease, even if bits/sec increases.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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