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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 847AAC433E0 for ; Tue, 9 Mar 2021 09:39:45 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id EA26E6523D for ; Tue, 9 Mar 2021 09:39:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA26E6523D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40666 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lJYq8-0007jw-0T for qemu-devel@archiver.kernel.org; Tue, 09 Mar 2021 04:39:44 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35126) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lJYo2-0006m8-HK for qemu-devel@nongnu.org; Tue, 09 Mar 2021 04:37:34 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:31035) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lJYo0-00010w-05 for qemu-devel@nongnu.org; Tue, 09 Mar 2021 04:37:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615282651; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=x6VqVhZmPKO6OAxZyXg1r4CUQMlH1kLy9P5mmJEAz1E=; b=RIdKSNO8K0XM52i0P5cSrEv/rCh65GC8urRhizrr8ysxd/muUtwPtRPloZMzmaGg7R4Dlj N53TkUKwkobJS8bQ+mGBuakHdnEn4bbXxMpan2kbHcOOnxelGQmaIghtP3kqboLeEasOP5 PiW8T5sTniUqDZVyE0lY7+YRzKuT414= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-470-Akc0huDPOK-8M6IUpTTczA-1; Tue, 09 Mar 2021 04:37:29 -0500 X-MC-Unique: Akc0huDPOK-8M6IUpTTczA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 080021084D68; Tue, 9 Mar 2021 09:37:28 +0000 (UTC) Received: from merkur.fritz.box (ovpn-114-169.ams2.redhat.com [10.36.114.169]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E378D6062F; Tue, 9 Mar 2021 09:37:19 +0000 (UTC) Date: Tue, 9 Mar 2021 10:37:18 +0100 From: Kevin Wolf To: Akihiko Odaki Subject: Re: [PATCH v2] block/file-posix: Optimize for macOS Message-ID: <20210309093718.GA5798@merkur.fritz.box> References: <20210305121748.65173-1-akihiko.odaki@gmail.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , pkrempa@redhat.com, qemu-block@nongnu.org, Markus Armbruster , qemu Developers , Max Reitz , Konstantin Nazarov , Stefan Hajnoczi , John Snow , dgilbert@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 09.03.2021 um 05:52 hat Akihiko Odaki geschrieben: > 2021年3月9日(火) 0:37 Akihiko Odaki : > > > > 2021年3月9日(火) 0:17 Stefan Hajnoczi : > > > > > > The live migration compatibility issue is still present. Migrating to > > > another host might not work if the block limits are different. > > > > > > Here is an idea for solving it: > > > > > > Modify include/hw/block/block.h:DEFINE_BLOCK_PROPERTIES_BASE() to > > > support a new value called "host". The default behavior remains > > > unchanged for live migration compatibility but now you can use "host" if > > > you know it's okay but don't care about migration compatibility. > > > > > > The downside to this approach is that users must explicitly say > > > something like --drive ...,opt_io_size=host. But it's still better than > > > the situation we have today where user must manually enter values for > > > their disk. > > > > > > Does this sound okay to everyone? > > > > > > Stefan > > > > I wonder how that change affects other block drivers implementing > > bdrv_probe_blocksizes. As far as I know, the values they report are > > already used by default, which is contrary to the default not being > > "host". > > > > Regards, > > Akihiko Odaki > > Let me suggest a variant of Stefan's approach: > > Modify include/hw/block/block.h:DEFINE_BLOCK_PROPERTIES_BASE() to > support a new value called "host". The default values for block size > properties may be "host" or not, but they should be consistent. If > they are "host" by default I'm not sure if it's a good idea, but maybe we could make it so that the default is "host" only as long as you didn't specify -nodefaults? Then libvirt would automatically keep the old behaviour (because it always sets -nodefaults) and manual invocations would usually get the new one. Of course, when I start with "I'm not sure if it's a good idea", it's usually not, but I wanted to share the thought anyway... > add global properties which sets > discard_granularity and opt_io_size to the old default to > hw_compat_5_2 in hw/core/machine.c. Otherwise, add global properties > which sets logical_block_size and physical_block_size to "host". Would we have to do this for explicitly for every single block device in the tree? That sounds like a lot of cases and therefore rather error prone. > Does it sound good? I'd also like to know others opinions for the > default value ("host" or something else). I prefer "host" as the > default a little because those who need live migration should be > careful enough to set proper configurations for each device. We may > also assist users who need live migration by adding a property which > defaults all block size properties to something else "host". Adding new requirements is always a bit problematic. Live migration works fine today without specifying these properties, so users will expect it to keep working. If live migration were a new feature and we required the options from the start, it would be different. Kevin