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 7A9DACA1013 for ; Thu, 18 Sep 2025 15:53:26 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uzGwC-0006s3-Is; Thu, 18 Sep 2025 11:52:48 -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 1uzGw9-0006rV-R3 for qemu-devel@nongnu.org; Thu, 18 Sep 2025 11:52:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uzGw7-0006mi-Kk for qemu-devel@nongnu.org; Thu, 18 Sep 2025 11:52:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758210762; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=J2SF7btJxVeohr0vewYvPCSWQbbVw+SiGQo4tYA5B6I=; b=EctAOWk+9e5iKmS7bnECaMzw9I8FcrzRhMuuSmuIufEtnveLz2dUK16bJcn+6hF8vsijHw DdTlKiop3XoZwmr8+vSmUyKXMZKI4oYWakFCHIFVni3PkKz10K9u39MCkjI59nqUqJt2+t xmcK7jejwvJjItHhw4viIMBgssLhG18= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-682-nH6pB2EkOIO8JDGCZt0tFQ-1; Thu, 18 Sep 2025 11:52:35 -0400 X-MC-Unique: nH6pB2EkOIO8JDGCZt0tFQ-1 X-Mimecast-MFC-AGG-ID: nH6pB2EkOIO8JDGCZt0tFQ_1758210754 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1908918002C1; Thu, 18 Sep 2025 15:52:34 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.161]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 85C3319560BB; Thu, 18 Sep 2025 15:52:32 +0000 (UTC) Date: Thu, 18 Sep 2025 16:52:29 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: Juraj Marcin , qemu-devel@nongnu.org, Fabiano Rosas , Jiri Denemark Subject: Re: [PATCH] migration: Apply migration specific keep-alive defaults to inet socket Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.133.124; 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=-0.005, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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 Thu, Sep 18, 2025 at 11:10:49AM -0400, Peter Xu wrote: > On Thu, Sep 18, 2025 at 03:45:21PM +0100, Daniel P. Berrangé wrote: > > There needs to be a way to initiate post-copy recovery regardless > > of whether we've hit a keepalive timeout. Especially if we can > > see one QEMU in postcopy-paused, but not the other side, it > > doesn't appear to make sense to block the recovery process. > > > > The virDomainJobCancel command can do a migrate-cancel on the > > src, but it didn't look like we could do the same on the dst. > > Unless I've overlooked something, Libvirt needs to gain a way > > to explicitly force both sides into the postcopy-paused state, > > and thus be able to immediately initiate recovery. > > Right, if libvirt can do that then problem should have been solved too. > > > I'm fine with turning on keepalives on the socket, but IMHO the > > out of the box behaviour should be to honour the kernel default > > tunables unless the admin decides they want different behaviour. > > I'm not seeing a rational for why the kernel defaults should be > > forceably overridden in QEMU out of the box. > > IMHO the rational here is that the socket here is in a special state and > for special purpose. So we're not trying to change anything globally for > qemu (without knowing what the socket is), but only this specific type of > socket that is used for either precopy or postcopy live migrations. > > It's special because it's always safe to have a more aggresive > disconnection, and might be preferred versus very lengthy hangs (if > assuming libvirt doesn't yet have way to stop the hang), especially for a > postcopy phase. I've already described up-thread that it is not guaranteed safe to have aggressive disconnection. It is often safe, but there is definitely non-negligible risk in prematurely terminating a migration connection. 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 :|