Re: [Qemu-devel] [PATCH v3 3/3] nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH

[Eric Blake]

On 7/25/19 5:05 AM, Vladimir Sementsov-Ogievskiy wrote:
> This helps to avoid extra io, allocations and memory copying.
> We assume here that CMD_CACHE is always used with copy-on-read, as
> otherwise it's a noop.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
>  nbd/server.c | 43 +++++++++++++++++++++++++++++++++++--------
>  1 file changed, 35 insertions(+), 8 deletions(-)

libnbd is able to test NBD_CMD_CACHE requests, and I've confirmed that
behavior looks sane under requests issued that way.  I'm wondering if
qemu-io should also be able to drive this mode of operation, so that we
can give it iotest coverage without depending on libnbd.

Reviewed-by: Eric Blake <address@hidden>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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