Messages in this thread | | | Date | Thu, 16 Jun 2011 10:09:01 +0100 | Subject | Re: [ANNOUNCE] Native Linux KVM tool v2 | From | Stefan Hajnoczi <> |
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On Thu, Jun 16, 2011 at 8:24 AM, Ingo Molnar <mingo@elte.hu> wrote: > - executing AIO in the vcpu thread eats up precious vcpu execution > time: combined QCOW2 throughput would be limited by a single > core's performance, and any time spent on QCOW2 processing would > not be spent running the guest CPU. (In such a model we certainly > couldnt do more intelligent, CPU-intense storage solutions like on > the fly compress/decompress of QCOW2 data.)
This has been a problem in qemu-kvm. io_submit(2) steals time from the guest (I think it was around 20us on the system I measured last year).
Add the fact that the guest kernel might be holding a spinlock and it becomes a scalability problem for SMP guests.
Anything that takes noticable CPU time should be done outside the vcpu thread.
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