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Re: [Qemu-block] [PATCH V2 0/8] add Qcow2 compress format extension

From: Peter Lieven
Subject: Re: [Qemu-block] [PATCH V2 0/8] add Qcow2 compress format extension
Date: Mon, 10 Jul 2017 14:36:15 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1

Am 29.06.2017 um 12:57 schrieb Peter Lieven:
this adds a create option for Qcow2 images to specify the compression format
and level for compressed clusters. The series adds 2 algorithms to choose from:
zlib and lzo. zlib is the current default, but with unoptimal settings.
If no compress.format option is specified the old zlib with the old parameters
is used and the created images are backwards compatible with older QEMU version.
As soon as a compression format is specified a new compress format header 
is written and the Qcow2 images are incompatible with older QEMU versions.

Some numbers for an uncompressed Debian 9 QCOW2 image (size 1148MB):

compress.format     compress time    compressed size   decompress time
none                35.7s            339MB             3.4s
zlib (default)      30.5s            320MB             3.2s
zlib (level 1)      12.8s            348MB             3.2s
lzo                  4.2s            429MB             1.6s

Changes V1->V2:
   - split the series into more patches
   - added an qapi scheme for the compression settings
   - renamed compression_algorithm to compress.format and added compress.level+
   - updated the header extension to carry a variable extra payload and compress
   - removed extra reservations for header extensions
   - added missing lzo_init and fixed compress overhead for lzo

Peter Lieven (8):
   docs: add compress format extension to qcow2 spec
   qapi: add compress parameters to Qcow2 Blockdev options
   block/qcow2: parse compress create options
   qemu-img: add documentation for compress settings
   block/qcow2: read and write the compress format extension
   block/qcow2: optimize qcow2_co_pwritev_compressed
   block/qcow2: start using the compress format extension
   block/qcow2: add lzo compress format

  block/qcow2-cluster.c     |  73 +++++++++++-----
  block/qcow2.c             | 219 +++++++++++++++++++++++++++++++++++++++-------
  block/qcow2.h             |  33 +++++--
  configure                 |   2 +-
  docs/interop/qcow2.txt    |  43 ++++++++-
  include/block/block_int.h |   2 +
  qapi/block-core.json      |  54 +++++++++++-
  qemu-img.texi             |  22 +++++
  8 files changed, 384 insertions(+), 64 deletions(-)


had anyone had a chance to look at the updated specs?



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