From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49500) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cxUua-0001P6-TI for qemu-devel@nongnu.org; Mon, 10 Apr 2017 04:43:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cxUua-00039W-3e for qemu-devel@nongnu.org; Mon, 10 Apr 2017 04:43:00 -0400 Date: Mon, 10 Apr 2017 10:42:50 +0200 From: Kevin Wolf Message-ID: <20170410084250.GC4883@noname.redhat.com> References: <20170406150148.zwjpozqtale44jfh@perseus.local> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="SLDf9lqlvOQaIe6s" Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: Alberto Garcia , qemu-devel@nongnu.org, qemu-block@nongnu.org, Stefan Hajnoczi --SLDf9lqlvOQaIe6s Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Am 07.04.2017 um 19:10 hat Max Reitz geschrieben: > One case I'd be especially interested in are of course 4 kB subclusters > for 64 kB clusters (because 4 kB is a usual page size and can be > configured to be the block size of a guest device; and because 64 kB > simply is the standard cluster size of qcow2 images nowadays[1]...). Why should the current default cluster size be an argument for anything? 64k is a tradeoff between small COW size and large allocation granularity that seemed to work well (and it used to be the maximum cluster size originally, so it seemed safer than 128k). With subclusters, we have a completely different situation and need to find a new default that works best. I'm relatively sure that 64k are too small under the new conditions. Also, undefined reference: [1] (I was hoping to find a better argument there...) Kevin --SLDf9lqlvOQaIe6s Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJY60WKAAoJEH8JsnLIjy/WLpcQAJZh7SaLlh98FTPKons1V3OK 9WiwW+iA3TK8UDOuGmYotNQlf+MmnX5E4MOMvdFV0sIzAtMK3NsIv/RLdVT5L91T nCA96z3qi6RQCFPJKzt2VHjCk9KX8+vJXAGicG8CsWobAKMi9CXkOEhhrw17+5HB G4apWk0/EMutji8u/q4yX2m0ZwpPNy8tPCpDvvID7EIZv1kpPKBewk5zkkdQv+K0 XeCKQ0V3ZH44TMVY2iFOBeKGUl8/CcdImK3sFTMTYs0UMjZVkGY7P/t5RLf+4O4a F7P3y8OGVLnOd+N8rXzoVeBVFRIZJwef0yGpnGBCmymOrNALf5Gm0IiOfEOlkcCZ nDAZ8D2kC1hq3xfV3fidJ8avNBnzpXdz0sWD4QS4FOYr2bAkCSpf22eUr7vrMmOG 2YkuxzoGc96MpXaTYaXjliJvO1UpSTVoIH6FC2Mr3UeXPks4LMtbDOn5P9taHhM2 u7P+tcrPXBEFFFI6TYPBloYBeBeFvc/VdNs9yN3ZSExyIp42KnhrreekCWzsR2VD xz27J1oElqcKCdydC+WLPuc6hqz0DFLYLQ2xKM/z6fQURM8QZhyLFtUhLAcCUaiZ T2k/PPCis8BxQVyGzXF8QHdZKcLKdQ/aON5RdO9+uWzhMK1TkX2oNhK42SfmYrPi FqVm6Os5r6Mblu5INefQ =iWEy -----END PGP SIGNATURE----- --SLDf9lqlvOQaIe6s--