From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5F3DDC25B47 for ; Wed, 25 Oct 2023 09:08:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qvZrk-0003lJ-IS; Wed, 25 Oct 2023 05:07:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qvZrc-0003kC-VR for qemu-devel@nongnu.org; Wed, 25 Oct 2023 05:07:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qvZrY-00061k-RP for qemu-devel@nongnu.org; Wed, 25 Oct 2023 05:07:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698224859; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=iYg1r8/Z83qTYLjWQeSnXy7sCAcI6WeAKSsgr+s8VdI=; b=caTVhxP6AnIol4as56VO8dt1U3f/FrLZzQJP6fStND/n/qAhoaFOdPdCOR+6ad/M41HU2G NIAQHcIC8cbjoLFscb7lcGgksddgWdbXLNev6IJiRkmKam7BsncVMDt82BW1Z4tMocVD1G bpNGlnefE9lTKrOHuR+5X6ezKxwDV84= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-99-_rGqnmFuPXKbq_ErOsgcKQ-1; Wed, 25 Oct 2023 05:07:36 -0400 X-MC-Unique: _rGqnmFuPXKbq_ErOsgcKQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BBF7A1C0515D; Wed, 25 Oct 2023 09:07:35 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.154]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 697BC8C0B; Wed, 25 Oct 2023 09:07:34 +0000 (UTC) Date: Wed, 25 Oct 2023 10:07:32 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Fabiano Rosas Cc: qemu-devel@nongnu.org, armbru@redhat.com, Juan Quintela , Peter Xu , Leonardo Bras , Claudio Fontana , Eric Blake Subject: Re: [PATCH v2 28/29] migration: Add direct-io parameter Message-ID: References: <20231023203608.26370-1-farosas@suse.de> <20231023203608.26370-29-farosas@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231023203608.26370-29-farosas@suse.de> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Oct 23, 2023 at 05:36:07PM -0300, Fabiano Rosas wrote: > Add the direct-io migration parameter that tells the migration code to > use O_DIRECT when opening the migration stream file whenever possible. > > This is currently only used for the secondary channels of fixed-ram > migration, which can guarantee that writes are page aligned. When you say "secondary channels", I presume you're meaning that the bulk memory regions will be written with O_DIRECT, while general vmstate will use normal I/O on the main channel ? If so, could we explain that a little more directly. Having a mixture of O_DIRECT and non-O_DIRECT I/O on the same file is a little bit of an unusual situation. It will work for us because we're writing to different regions of the file in each case. Still I wonder if it would be sane in the outgoing case to include a fsync() on the file in the main channel, to guarantee that the whole saved file is on-media at completion ? Or perhaps suggest in QAPI that mgmts might consider doing a fsync themselves ? With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|