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Date: Wed, 04 Feb 2015 16:04:33 +0100
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Subject: Re: [Qemu-devel] RFC: Universal encryption on QEMU I/O channels
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To: "Daniel P. Berrange" <berrange@redhat.com>
Cc: qemu-devel@nongnu.org



On 04/02/2015 15:34, Daniel P. Berrange wrote:
> > GIO doesn't provide writev either, so it's not a good match for
> > non-encrypted migration, which really tries hard to do no copies in
> > userspace.
> 
> Ok, maybe RDMA will still need QEMUFile, but for non-encrypted TCP
> I'd hope to be able to achieve zero-copy with the new API too - it
> would certainly be my intention/goal.

For GIO/GIOChannel, you'd have to choose between zerocopy and many
syscalls, or one copy and few syscalls.  Since every page has two iov
entries, one of which is just 8 bytes, one copy and few syscalls is
probably faster---but still only half the speed of writev.

Paolo