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 B0A37CE79D0 for ; Wed, 20 Sep 2023 13:23:29 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qixAA-0004Th-9c; Wed, 20 Sep 2023 09:22:42 -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 1qixA7-0004TE-U9 for qemu-devel@nongnu.org; Wed, 20 Sep 2023 09:22:39 -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 1qixA5-0002Ut-R8 for qemu-devel@nongnu.org; Wed, 20 Sep 2023 09:22:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695216156; 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=PFfi7pjxQSw9VVLKXr6BlE+iroOPsG5xuhorKXSb3TY=; b=YVdKve7giPUoIaqyturqMNnuaQ/Uf1RH42+S+eUH4T9kQCw5kpBiM63v50Lhv5dHt6uz8Q +QAlrMQTgPRu6Rci+zzH8qrtc+jo+ygw/L6KAukptzhTxyTy82lzHrbudh4XQM7yOqzAhc bjBVezvbPUXpd+YtqHpa0WugLFyya7c= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-183-Y-RMt2MhNg2Q5hrNerNczw-1; Wed, 20 Sep 2023 09:22:35 -0400 X-MC-Unique: Y-RMt2MhNg2Q5hrNerNczw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C1E3D101A550; Wed, 20 Sep 2023 13:22:34 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 89C1540C6EBF; Wed, 20 Sep 2023 13:22:34 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 9008521E6900; Wed, 20 Sep 2023 15:22:33 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: Peter Xu , qemu-devel@nongnu.org, quintela@redhat.com, leobras@redhat.com, Li Zhijian Subject: Re: [PATCH 00/52] migration/rdma: Error handling fixes References: <20230918144206.560120-1-armbru@redhat.com> Date: Wed, 20 Sep 2023 15:22:33 +0200 In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Tue, 19 Sep 2023 19:29:32 +0100") Message-ID: <8734z9f086.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 writes: > On Tue, Sep 19, 2023 at 12:49:46PM -0400, Peter Xu wrote: >> On Mon, Sep 18, 2023 at 04:41:14PM +0200, Markus Armbruster wrote: >> > Oh dear, where to start. There's so much wrong, and in pretty obvious >> > ways. This code should never have passed review. I'm refraining from >> > saying more; see the commit messages instead. >> >=20 >> > Issues remaining after this series include: >> >=20 >> > * Terrible error messages >> >=20 >> > * Some error message cascades remain >> >=20 >> > * There is no written contract for QEMUFileHooks, and the >> > responsibility for reporting errors is unclear >>=20 >> Even being removed.. because no one is really extending that.. >>=20 >> https://lore.kernel.org/all/20230509120700.78359-1-quintela@redhat.com/#t > > One day (in another 5-10 years) I still hope we'll get to > the point where QEMUFile itself is obsolete :-) Getting > rid of QEMUFileHooks is a great step in that direction. > Me finishing a old PoC to bring buffering to QIOChannel > would be another big step. > > The data rate limiting would be the biggest missing piece > to enable migration/vmstate logic to directly consume > a QIOChannel. > > Eliminating QEMUFile would help to bring Error **errp > to all the vmstate codepaths. Sounds like improvement to me. >> > * There seem to be no tests whatsoever >>=20 >> I always see rdma as "odd fixes" stage.. for a long time. But maybe I w= as >> wrong. To be honest, it doesn't look or smell maintained to me. More like thrown over the fence and left to rot. Given the shape it is in, I wouldn't let friends use it in production. > In the MAINTAINERS file RDMA still get classified as formally > supported under the migration maintainers. I'm not convinced > that is an accurate description of its status. I tend to agree > with you that it is 'odd fixes' at the very best. Let's fix MAINTAINERS not to raise unrealistic expectations. > Dave Gilbert had previously speculated about whether we should > even consider deprecating it on the basis that latest non-RDMA > migration is too much better than in the past, with multifd > and zerocopy, that RDMA might not even offer a significant > enough peformance win to justify. I provided approximately 52 additional arguments for deprecating it :) >> Copying Zhijian for status of rdma; Zhijian, I saw that you just replied= to >> the hwpoison issue. Maybe we should have one entry for rdma too, just l= ike >> colo? > > With regards, > Daniel