Re: Zero-copy block driver?

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2011/1/29 Darko PetroviÄ <darko.b.petrovic@xxxxxxxxx>:
> Could you please tell me if it is possible to use a block driver that
> completely avoids the guest kernel and copies block data directly to/from
> the given buffer in the guest userspace?
> If yes, how to activate it? If not... why not? :)

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
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