Re: Zero-copy block driver?

["Darko Petrović" <darko.b.petrovic@gmail.com>]

Thanks for your help. Actually, I am more interested in doing it from 
the outside, if possible (I am not allowed to change the application 
code). Can the guest be tricked by KVM somehow, using the appropriate 
drivers? Just to clear it out, copying to/from a host buffer is fine, I 
just want to avoid having guest buffers.

Cheers!
Darko

On 01/29/2011 10:49 AM, Stefan Hajnoczi wrote:
> Inside the guest, open files using the O_DIRECT flag. This tells the
> guest kernel to avoid the page cache when possible, enabling
> zero-copy.  You need to use aligned memory buffers and perform I/O in
> multiples of the block size.
>
> See the open(2) man page for details.  Make sure you really want to do
> this, most applications don't.
>
> Stefan