Re: [Qemu-devel] [PATCH 4/4] block/qcow2: add zlib-fast compression algorithm

[Peter Lieven]

Am 27.06.2017 um 14:53 schrieb Eric Blake:
> On 06/27/2017 07:34 AM, Peter Lieven wrote:
> > this adds support for optimized zlib settings which almost
> Start sentences with a capital.
>
> > tripples the compression speed while maintaining about
> s/tripples/triples/
>
> > the same compressed size.
> >
> > Signed-off-by: Peter Lieven <address@hidden>
> > ---
> >   block/qcow2-cluster.c |  3 ++-
> >   block/qcow2.c         | 11 +++++++++--
> >   block/qcow2.h         |  1 +
> >   qemu-img.texi         |  1 +
> >   4 files changed, 13 insertions(+), 3 deletions(-)
> >
> > +++ b/block/qcow2.h
> > @@ -173,6 +173,7 @@ typedef struct Qcow2UnknownHeaderExtension {
> >   enum {
> >       QCOW2_COMPRESSION_ZLIB          = 0xC0318301,
> >       QCOW2_COMPRESSION_LZO           = 0xC0318302,
> > +    QCOW2_COMPRESSION_ZLIB_FAST     = 0xC0318303,
> Back to my comments on 1/4 - we MUST first get the qcow2 specification
> right, rather than adding undocumented headers in the code.  And I still
> think you only need one variable-length header extension for covering
> all possible algorithms, rather than one header per algorithm.  Let's
> get the spec right first, before worrying about the code implementing
> the spec.

Okay, I think someone came up with the idea to have an optional
header per algorithm, but you are right one header with an optional
parameter payload will also do.

I will split the spec change to a separate patch in V2 to make it easier
to respin.

Thanks,
Peter