From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56127) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUey0-0007EE-4M for qemu-devel@nongnu.org; Fri, 20 Jan 2017 14:35:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cUexv-0001JS-Ad for qemu-devel@nongnu.org; Fri, 20 Jan 2017 14:35:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33446) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cUexu-0001Hw-QT for qemu-devel@nongnu.org; Fri, 20 Jan 2017 14:35:15 -0500 References: <20161214150840.10899-1-alex@alex.org.uk> <442dcfe4-8704-2898-655e-da383a0caf76@virtuozzo.com> <220990D0-ACB6-4F25-BADF-63898FE71BED@alex.org.uk> From: Eric Blake Message-ID: <0654e27f-9c2f-993c-befd-1f1e8e75aabf@redhat.com> Date: Fri, 20 Jan 2017 13:35:10 -0600 MIME-Version: 1.0 In-Reply-To: <220990D0-ACB6-4F25-BADF-63898FE71BED@alex.org.uk> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="8vNEchuKpJDuSeioMELa7VErvIRVwCTSj" Subject: Re: [Qemu-devel] [PATCH] Further tidy-up on block status List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Bligh , Vladimir Sementsov-Ogievskiy Cc: "nbd-general@lists.sourceforge.net" , Kevin Wolf , "Denis V . Lunev" , "qemu-devel@nongnu.org" , Pavel Borzenkov , "Stefan stefanha@redhat. com" , Paolo Bonzini , Markus Pargmann , Wouter Verhelst , John Snow This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --8vNEchuKpJDuSeioMELa7VErvIRVwCTSj From: Eric Blake To: Alex Bligh , Vladimir Sementsov-Ogievskiy Cc: "nbd-general@lists.sourceforge.net" , Kevin Wolf , "Denis V . Lunev" , "qemu-devel@nongnu.org" , Pavel Borzenkov , "Stefan stefanha@redhat. com" , Paolo Bonzini , Markus Pargmann , Wouter Verhelst , John Snow Message-ID: <0654e27f-9c2f-993c-befd-1f1e8e75aabf@redhat.com> Subject: Re: [Qemu-devel] [PATCH] Further tidy-up on block status References: <20161214150840.10899-1-alex@alex.org.uk> <442dcfe4-8704-2898-655e-da383a0caf76@virtuozzo.com> <220990D0-ACB6-4F25-BADF-63898FE71BED@alex.org.uk> In-Reply-To: <220990D0-ACB6-4F25-BADF-63898FE71BED@alex.org.uk> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 01/20/2017 12:00 PM, Alex Bligh wrote: >=20 >> On 20 Jan 2017, at 17:04, Vladimir Sementsov-Ogievskiy wrote: >> >> About extents: is 32bit length enough? We will have to send 4096 for e= mpty 16tb disk.. >=20 > The nbd protocol uniformly uses 32 bit lengths (for better or for worse= ). This is baked into the specification heavily. >=20 > I'm not sure sending 4,096 items for an empty 16TB disk is any great ha= rdship to be honest. If it truly matters, an idea that has already been floated on the list is to add a new NBD_CMD_FLAG_SCALE (or some other spelling) that states that a particular command is sending lengths scaled by a particular factor (by the block size? obviously it would have to be better specified). Under this idea, the scaling factor would allow you to report larger extents for fewer back-and-forth operations, but it gets tricky if the scaling is allowed to get larger than the minimum granularity between extent changes. The other idea that has been floated is a way to report whether the entire export is known to be all-zero content at the time the client connects, which would trade 4096+ queries (you'd actually have to do more than 4096 queries, since length is < 4G, not <=3D 4G) with a single piece of information at the time the client connects. Either way, discussion on such enhancements are probably worth a new thre= ad. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --8vNEchuKpJDuSeioMELa7VErvIRVwCTSj Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJYgmZuAAoJEKeha0olJ0NqjMcH/3KGxNPE/Hwl2BQZyzB138aG 9KnbOc3hqB6FIO6J4MThiyJHZK+rkuND5J4+lkGhim1ASRw3JkwlNFQcX2XVUyi2 okiFj1g8TtfVtixkYzMfdfH98bou+nWlf1/aw1dcHVKDrLzCOro3FeIUVWcHratX 1SrLvcs1Y3TfIde+5L4i5JvwpEvI+91Q1uuhqrhWoZEh264kmYgHtMdlGKKWJHzV DL2EOSTAV8A/39mzHDga9SrPAXHlLNJPB/e3jd1xU4H0mQXmPMAqVvPdVqLTmGN4 Kr1jAuWAGISGvC5QsizLU2euDKSs/cr7x8O06CzCHIQRs3kyeOCv6H28iI3tKBc= =iDpI -----END PGP SIGNATURE----- --8vNEchuKpJDuSeioMELa7VErvIRVwCTSj--