From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54932) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zgu38-0008OF-Fz for qemu-devel@nongnu.org; Tue, 29 Sep 2015 08:30:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zgu32-0006bi-87 for qemu-devel@nongnu.org; Tue, 29 Sep 2015 08:30:26 -0400 References: <1442589793-7105-1-git-send-email-mreitz@redhat.com> <1442589793-7105-18-git-send-email-mreitz@redhat.com> <20150922141701.GD3999@noname.str.redhat.com> <56016CF5.8030709@redhat.com> From: Eric Blake Message-ID: <560A844C.6020801@redhat.com> Date: Tue, 29 Sep 2015 06:30:04 -0600 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="TO88bA2wvUN9BQJob7qqs3EKfQSX6fV8V" Subject: Re: [Qemu-devel] [PATCH v5 17/38] block: Add BlockBackendRootState List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alberto Garcia , Max Reitz , Kevin Wolf Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, Markus Armbruster , Stefan Hajnoczi , John Snow This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --TO88bA2wvUN9BQJob7qqs3EKfQSX6fV8V Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 09/29/2015 05:17 AM, Alberto Garcia wrote: > On Tue 22 Sep 2015 05:00:05 PM CEST, Max Reitz wrote: >=20 >>> The correct way to solve this seems to be that each BB has its own >>> I/O throttling filter. Actually, if we could lift the throttling code= >>> to BlockBackend, that might solve the problem. >> >> So yes, as long as we have throttling on the BDS level, something may >> always break when having multiple BBs per BDS, because you'd probably >> want throttling to be on the BB level. But lifting that doesn't seem a= >> trivial task, and I don't really know whether I want this in this >> series. >> >> Especially considering that right now you cannot have multiple BBs per= >> BDS. >> >> All in all: Yes, before we allow multiple BBs per BDS we want >> throttling to be on the BB level. But this is nothing that should be >> done in or for this series, since right now we do not allow multiple >> BBs per BDS. >=20 > I agree that it makes sense to move throttling to the BB level. It's > probably not trivial but I don't think it's too complex either. I can > give it a look once this series has been merged. Ultimately, I think we want throttling at both levels. I can make the argument that in a cloud, a guest should not be able to consume more than X resources (throttling at the BB, regardless of what BDS tree it is associated with); but I can also argue that I may want to throttle specific BDS (a backing chain with network backing file and local active file: throttle the backing file to limit network traffic, and the guest gets faster as it moves more local; or conversely, a common backing file and one-off guest: throttle the active layer to do performance analysis of the bottlenecks where the guest differs from the common backing layer)= =2E --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --TO88bA2wvUN9BQJob7qqs3EKfQSX6fV8V 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/ iQEcBAEBCAAGBQJWCoRMAAoJEKeha0olJ0NqjfoH+wdJ99PST4YRj0464dE2Voke jun5oKwy6yyWNJJx66TEL3/KlfgsYe3XK+/x+/+idB9kdtilwE5UowvKLnBe8I6W ufIZ57lkDGtEWBHA7pAO6in5Vp0i9Z5CH2C/E8HMqFMkYnQCuk0E6xpZFBlu43Bt tI2joLvYLD+RbOQHbXcKsVcAchGwhgdHIblh4gDqLBlxbjTuxsdxr85WjFZZ163O +RmExQOlfldFYmut7/Gf2uOqAkUpcWYopdkbNFNdMw8nLqS+qoRrnVyX+qhPOU8c A17VTG4voOPybug+I3PJ+ZDwO3U0Y5oxxvm8NDsrLz9IJM6/vfXyumXiEqQznxk= =gopj -----END PGP SIGNATURE----- --TO88bA2wvUN9BQJob7qqs3EKfQSX6fV8V--