From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48732) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z38kK-000802-Jv for qemu-devel@nongnu.org; Thu, 11 Jun 2015 16:06:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z38kH-0003ua-8W for qemu-devel@nongnu.org; Thu, 11 Jun 2015 16:06:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59073) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z38kH-0003sm-2q for qemu-devel@nongnu.org; Thu, 11 Jun 2015 16:06:37 -0400 Date: Thu, 11 Jun 2015 21:06:32 +0100 From: Stefan Hajnoczi Message-ID: <20150611200632.GA29013@stefanha-thinkpad.redhat.com> References: <1433776886-27239-1-git-send-email-vsementsov@virtuozzo.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="OgqxwSJOaUobr8KG" Content-Disposition: inline In-Reply-To: <1433776886-27239-1-git-send-email-vsementsov@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH v2 RFC 0/8] block: persistent dirty bitmaps List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vladimir Sementsov-Ogievskiy Cc: kwolf@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com, den@openvz.org, jsnow@redhat.com --OgqxwSJOaUobr8KG Content-Type: text/plain; charset=us-ascii Content-Disposition: inline The load/store API is not scalable when bitmaps are 1 MB or larger. For example, a 500 GB disk image with 64 KB granularity requires a 1 MB bitmap. If a guest has several disk images of this size, then multiple megabytes must be read to start the guest and written out to shut down the guest. By comparison, the L1 table for the 500 GB disk image is less than 8 KB. I think something like qcow2-cache.c or metabitmaps should be used to lazily read/write persistent bitmaps. That way only small portions need to be read/written at a time. Stefan --OgqxwSJOaUobr8KG Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJVeepIAAoJEJykq7OBq3PIFsAH/36FHO7el/zNcU6i2H0cQaxH UFKIomJax9t1qTwccCZN2iTOAPt0tW+d9sBW0xlkjmvFJV5YFatWGFiAvF+wohs+ Spd0OD7MRUfDRG3g4pzCmCr2lUCbD2+nClDhu4BqUT/pAWg5gABzERpPJ+gIP1wQ 1ZXd06PjYHf4MNmIVt5iqcRCFBU3FcFyBULhAQGIIriU+r2pKh1WlSoizRbLtZks fBn1LmnwLo2B7MKO7yV+OOdNeAHxJzEka/Ilh3UNm7UaKTBWmCC5aQuKXVg6toNd wSjxLgpr4LcNyUjbFAXorPMlDMqkXMNoZTJbtBYraylzdHkAlNThYt0FQxEG2lU= =f6/l -----END PGP SIGNATURE----- --OgqxwSJOaUobr8KG--