From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42527) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1da6x5-0007UQ-JM for qemu-devel@nongnu.org; Tue, 25 Jul 2017 17:01:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1da6x4-00067L-J9 for qemu-devel@nongnu.org; Tue, 25 Jul 2017 17:01:11 -0400 References: <1500993699-19299-1-git-send-email-pl@kamp.de> <1500993699-19299-2-git-send-email-pl@kamp.de> <8f1f2bd2-4509-e603-218d-942859d6316f@kamp.de> From: Eric Blake Message-ID: <89ad7fdf-b6fe-cd96-10e4-7384cdcb1c77@redhat.com> Date: Tue, 25 Jul 2017 16:01:04 -0500 MIME-Version: 1.0 In-Reply-To: <8f1f2bd2-4509-e603-218d-942859d6316f@kamp.de> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ng3dEM8mNRa9VkOTiuX76sElc2B0cJBNw" Subject: Re: [Qemu-devel] [PATCH V5 01/10] specs/qcow2: add compress format extension List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, kwolf@redhat.com, lersek@redhat.com, den@openvz.org, mreitz@redhat.com, berrange@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --ng3dEM8mNRa9VkOTiuX76sElc2B0cJBNw From: Eric Blake To: Peter Lieven , qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, kwolf@redhat.com, lersek@redhat.com, den@openvz.org, mreitz@redhat.com, berrange@redhat.com Message-ID: <89ad7fdf-b6fe-cd96-10e4-7384cdcb1c77@redhat.com> Subject: Re: [PATCH V5 01/10] specs/qcow2: add compress format extension References: <1500993699-19299-1-git-send-email-pl@kamp.de> <1500993699-19299-2-git-send-email-pl@kamp.de> <8f1f2bd2-4509-e603-218d-942859d6316f@kamp.de> In-Reply-To: <8f1f2bd2-4509-e603-218d-942859d6316f@kamp.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 07/25/2017 03:29 PM, Peter Lieven wrote: >>> + deflate: Standard zlib deflate compression withou= t >>> + compression header >> Why did you name it "deflate" instead of "zlib" again? >=20 > zlib provides raw deflate encoding and gzip encoding both with and with= out header afaik. > We use raw deflate encoding without header in QEMU. And the name of the= algorithm is deflate. > I found it more appropriate than zlib. Okay, I can live with that. >=20 >> >>> + >>> + 14: compress_level (uint8_t) >>> + >>> + 0 =3D default compress level (valid for all forma= ts, default) >>> + >>> + Additional valid compression levels for deflate c= ompression: >>> + >>> + All values between 1 and 9. 1 gives best speed, 9= gives best >>> + compression. The default compression level is def= ined by zlib >>> + and currently defaults to 6. >>> + >>> + 15: compress_window_size (uint8_t) >>> + >>> + Window or dictionary size used by the compression= format. >>> + Currently only used by the deflate compression al= gorithm. >> What must this be set to for other algorithms? I guess we get to that= >> in later patches. >=20 > Its only used by the deflate algorithm. At this point we only have that= algorithm. > lzo has no such encoding. If we add e.g. lzma it has a dictionary size = which is > a power of two (typcial value would be 2^20). So for lzo, we should document that the field must be 0 (when we get to adding it). >=20 > Can you also have a look at the remainder of the series? It's on my list for 2.11 reviews, although 2.10 freeze stuff is taking priority, so it may be a few days yet. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org --ng3dEM8mNRa9VkOTiuX76sElc2B0cJBNw Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAll3sZAACgkQp6FrSiUn Q2q7SQf/U3hfdMRIlg4Yw0+KNuRJNhTQ1/4FNGEJk5I/isO6iOEHQoPJZByxLpeo ODgk93i0CnSSEUMCQcJgCxjDUOEnm9lPCaI+LlSV0NtzlKeTabirPp1RdHdNpnjn TGN/PfqIRj5RG1zx7SVO3gUqE0+YKROqtz2qFjGZhwe6AiYdYwWNUUabYYpEJ2qu KeimI9bosEnOtj+eZ0aibnIF9n4pE3M4okbdaUxWmco+9Sc8PY7TA0Cq/K/qszdo XPNWsbO/KhpB8PtoM0A2sPkgpTkHzR9+SuGBPlJg81oixrotHAF8EoWfXcY2NxQS UOLZOJYONGnJfasyWds/TD9Haoge7Q== =KQpe -----END PGP SIGNATURE----- --ng3dEM8mNRa9VkOTiuX76sElc2B0cJBNw--