From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56819) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dPqLu-0003Bh-NP for qemu-devel@nongnu.org; Tue, 27 Jun 2017 09:16:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dPqLt-0001uz-J6 for qemu-devel@nongnu.org; Tue, 27 Jun 2017 09:16:22 -0400 Date: Tue, 27 Jun 2017 14:16:05 +0100 From: "Daniel P. Berrange" Message-ID: <20170627131605.GG13634@redhat.com> Reply-To: "Daniel P. Berrange" References: <1498566850-7934-1-git-send-email-pl@kamp.de> <1498566850-7934-5-git-send-email-pl@kamp.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1498566850-7934-5-git-send-email-pl@kamp.de> Subject: Re: [Qemu-devel] [PATCH 4/4] block/qcow2: add zlib-fast compression algorithm List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: qemu-block@nongnu.org, kwolf@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, den@openvz.org, lersek@redhat.com On Tue, Jun 27, 2017 at 02:34:10PM +0200, Peter Lieven wrote: > this adds support for optimized zlib settings which almost > tripples the compression speed while maintaining about > the same compressed size. > > Signed-off-by: Peter Lieven > --- > block/qcow2-cluster.c | 3 ++- > block/qcow2.c | 11 +++++++++-- > block/qcow2.h | 1 + > qemu-img.texi | 1 + > 4 files changed, 13 insertions(+), 3 deletions(-) > diff --git a/qemu-img.texi b/qemu-img.texi > index 043c1ba..83a5db2 100644 > --- a/qemu-img.texi > +++ b/qemu-img.texi > @@ -627,6 +627,7 @@ The following options are available if support for the respective libraries > has been enabled at compile time: > > zlib Uses standard zlib compression (default) > + zlib-fast Uses zlib compression with optimized compression parameters This looks like a poor design from a future proofing POV. I would much rather see us introduce a more flexible modelling of compression at the QAPI layer which lets us have tunables for each algorith, in the same way that the qcow2 built-in encryption now has ability to set tunables for each algorithm. eg your "zlib-fast" impl which just uses zlib with a window size of -15 could be expressed as qemu-img create -o compress.format=zlib,compress.window=-15 > lzo Uses LZO1X compression Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|