Re: [ANNOUNCE] Native Linux KVM tool v2
From: Stefan Hajnoczi
Date: Thu Jun 16 2011 - 05:09:09 EST
On Thu, Jun 16, 2011 at 8:24 AM, Ingo Molnar <mingo@xxxxxxx> 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.
Stefan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/