From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:51079) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghH4s-0001Iu-4G for qemu-devel@nongnu.org; Wed, 09 Jan 2019 11:51:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ghH4r-0003cK-4c for qemu-devel@nongnu.org; Wed, 09 Jan 2019 11:51:38 -0500 Date: Wed, 9 Jan 2019 17:51:11 +0100 From: Kevin Wolf Message-ID: <20190109165111.GI4867@localhost.localdomain> References: <20190108194552.45453-1-vsementsov@virtuozzo.com> <20190109112311.GB4867@localhost.localdomain> <5ddd78e0-90ed-a6e5-c454-f1a2e44c1a37@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5ddd78e0-90ed-a6e5-c454-f1a2e44c1a37@redhat.com> Subject: Re: [Qemu-devel] [PATCH] file-posix: add rough-block-status parameter List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org, armbru@redhat.com, eblake@redhat.com, mreitz@redhat.com, fam@euphon.net, stefanha@redhat.com, den@openvz.org Am 09.01.2019 um 17:42 hat Paolo Bonzini geschrieben: > On 09/01/19 12:23, Kevin Wolf wrote: > > Also note that this is only metadata preallocation; full preallocation > > will still return allocated for the protocol layer and so it will always > > be slow. > > Full preallocation these days can create images with preallocated but > known-zero blocks, I think? That would defeat one of the main purposes of preallocation because it would still require COW and metadata updates on the first write. If there is demand, we could add something like preallocation=data where data clusters are preallocated but COW/metadata updates still happen at runtime, but so far nobody has asked for it. Not sure when you would use it either. Kevin