From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47869) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1coq06-0008Ry-Ep for qemu-devel@nongnu.org; Fri, 17 Mar 2017 07:24:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1coq05-0008VG-Lj for qemu-devel@nongnu.org; Fri, 17 Mar 2017 07:24:54 -0400 Date: Fri, 17 Mar 2017 19:24:46 +0800 From: Fam Zheng Message-ID: <20170317112446.GH13125@lemon.lan> References: <82d604c8-068a-aff4-6037-e3cd247b3588@redhat.com> <819af057-3777-dffc-4670-895b8265fd01@kamp.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] callout to *file in bdrv_co_get_block_status List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Peter Lieven , qemu block , "qemu-devel@nongnu.org" On Fri, 03/17 12:16, Paolo Bonzini wrote: > > > On 17/03/2017 12:11, Peter Lieven wrote: > >>> like VMDK or QCOW2 shouldn't we trust the information from the l2 tables in the VMDK or QCOW2? > >> It provides additional information, for example it works better with > >> prealloc=metadata. > > Okay, understood. Can you imagine of a away to conditionally avoid this second callout? In my case we have an additional > > lseek for each cluster. For a 20GB file this are approx. 327k calls to lseek. And if the file has no preallocated metadata > > it will likely not improve anything. And even if the metadata is prealloced what is the allocation status of the clusters? > > If the metadata is preallocated, cluster will (or should) show up as > zero, speeding up the copy. I think from qemu-img convert's perspective, it doesn't care about the *file status if the metadata already speaks, because, like you said, the data shows up as zeroes. In other words I think this can be optimized. Fam