Ingo Molnar wrote:
* Ingo Molnar <[email protected]> wrote:
dyntick-enabled guest:
- reduce the load on the host when the guest is idling
(currently an idle guest consumes a few percent cpu)
yeah. KVM under -rt already works with dynticks enabled on both the
host and the guest. (but it's more optimal to use a dedicated
hypercall to set the next guest-interrupt)
using the dynticks code from the -rt kernel makes the overhead of an
idle guest go down by a factor of 10-15:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2556 mingo 15 0 598m 159m 157m R 1.5 8.0 0:26.20 qemu
As usual, great news.
( for this to work on my system i have added a 'hyper' clocksource
hypercall API for KVM guests to use - this is needed instead of the
running-to-slowly TSC. )
What's the problem with the TSC? The only issue I'm aware of is that
the tsc might go backwards if the vcpu is migrated to another host cpu
(easily fixed).
A pv clocksource makes sense in any case.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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