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Re: [vfio-users] Speed tips requested





On Sun, Mar 26, 2017 at 6:33 AM, Patrick O'Callaghan <poc usb ve> wrote:
On Sun, 2017-03-26 at 10:58 +0100, Bronek Kozicki wrote:
> Assuming you use libvirt, make sure to use vCPU pinning. For disk access, try cache='writeback' io='threads'. If you switch to scsio-vfio, this will give you the ability to define queue length which might additionally improve IO. Also, try QCOW2 format for guest disk, it might enable some additional optimizations. However given you host seem to have little spare capacity, YMMV

Thanks. I'm already using CPU pinning as I said. The disk options are
both set to "hypervisor default" so I'll try changing them. I'd
configured the guest disk as 'raw' assuming that would be faster than
QCOW2 but I'll look into it.


Here's a link with some benchmarks. If configured correctly, QCOW2 can be more efficient than native i/o:

http://jrs-s.net/2013/05/17/kvm-io-benchmarking/ 

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