From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43472) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTO7y-0001k1-A0 for qemu-devel@nongnu.org; Thu, 14 Jun 2018 05:01:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fTO7s-0002C3-I2 for qemu-devel@nongnu.org; Thu, 14 Jun 2018 05:01:10 -0400 Date: Thu, 14 Jun 2018 11:00:55 +0200 From: Kevin Wolf Message-ID: <20180614090055.GB8564@localhost.localdomain> References: <20180613154711.12977-1-dplotnikov@virtuozzo.com> <20180613154711.12977-3-dplotnikov@virtuozzo.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="3MwIy2ne0vdjdPXF" Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH v0 2/2] qmp: add block-set-copy-on-read command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: Eric Blake , Denis Plotnikov , qemu-block@nongnu.org, armbru@redhat.com, famz@redhat.com, stefanha@redhat.com, jcody@redhat.com, qemu-devel@nongnu.org, den@virtuozzo.com, rkagan@virtuozzo.com, berto@igalia.com --3MwIy2ne0vdjdPXF Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Am 13.06.2018 um 18:41 hat Max Reitz geschrieben: > On 2018-06-13 18:02, Eric Blake wrote: > > On 06/13/2018 10:47 AM, Denis Plotnikov wrote: > >> The command enables/disables copy-on-read mode for VM's disk while > >> VM is running. > >> > >> This is needed when using external disk readers to shape access pattern > >> to the disk backend. > >> > >> Signed-off-by: Denis Plotnikov > >> --- > >=20 > > Deferring thoughts on the actual design for later; >=20 > But why? ;-) >=20 > This patch would definitely be superseded by a block reconfiguration > command (i.e. presumably one that makes reopen accessible over QMP). > With such a command, you could insert or remove a copy-on-read filter > node at any point in time. >=20 > Since we definitely want block graph configuration, I don't think we > want to add special commands now. I agree, and it seems that we get more and more use cases for a block reconfiguration commands. Only yesterday we talked about the "true" blockdev way for libvirt to implement I/O throttling. The result was that without reopen, we still need to use the old QMP command to set BlockBackend-based I/O throttling instead of using a filter node. So I'm eagerly awaiting Berto's promised patches for it. Kevin --3MwIy2ne0vdjdPXF Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIcBAEBAgAGBQJbIi7HAAoJEH8JsnLIjy/WAN4QAIF/7nvDdH6JSd9eIh0GvITj I5shA4B9JTIXb7PH2xhHpTuG5nGdXkIuBuKlN/zyXq1oAt2rhNlVqMyX32EQu2OA DBSwx6YNxbShaCQobyONwz0QRnlL/JS39q9BxWyT77LbTp3v6ar6y7bPFkeTUpXE 48l4ZNrl3L5ZaxAbZYR5mOShujbP4lxLun6bh0d8KFPLAaBn3IaRfXkV/MGNn8pR 8mWOKRFmVlTV0Wb3msDCdnC06wnioqeItp/wKpntLmXWCHcMcv74Ur7bMCmzIrPV c5RUmPghPQ0mURqCa8BJHBUT7vkrrW3KmJV6obNqF8smHj5uifPpun8X+A7Rzvpg pLxvatzl41dhNcm0ih9KcZgIeQ8cgZsswWDSG3iuAsnDJS5hneT0StQEXK1CUqKr V5qx+cL30eicjXNsmqLsdxCjFgonwA0Lx4bvVwERRgbuuJdaWJYH4pAY+hk6gBPs XUMOJr7m4YKrDJGPMuHRGz7dnZOWt4ji6AGbq77qsI9l98zKFmFiTMdTSTJse9LE 6COtlrIsXiSXoxdVCrcSkCVt5hsuoKhlP+B2WUGTByW94UmdwKshxB5+B5/MrXfW 6J6/FcftP1Q8sbB6c/XVLlY7KvulG7hAYg9Rsc4OdfihhlWW26+Wal2spJkhumoa A/sgXEc6OJEAwikFWKrk =OXL9 -----END PGP SIGNATURE----- --3MwIy2ne0vdjdPXF--