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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Mon, 30 Nov 2015 09:36:22 +0100
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Subject: Re: [Qemu-devel] [PATCH 07/40] virtio: slim down allocation of
 VirtQueueElements
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To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org



On 30/11/2015 04:24, Fam Zheng wrote:
> > +    for (i = 0; i < out_num; i++) {
> > +        elem->out_addr[i] = addr[i];
> > +        elem->out_sg[i] = iov[i];
> > +    }
>
> Isn't memcpy more efficient here? Otherwise looks good.

Probably not, out_num/in_num is usually very small, in fact one of them
is often 0 or 1.

For example the memcpy in address_space_rw is awfully inefficient.  This
is roughly the same.

Paolo