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 233E2C7618E for ; Wed, 26 Apr 2023 09:08:48 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1prb87-0004q4-Qe; Wed, 26 Apr 2023 05:08:03 -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 1prb80-0004m0-AX for qemu-devel@nongnu.org; Wed, 26 Apr 2023 05:07:57 -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 1prb7s-00038q-UF for qemu-devel@nongnu.org; Wed, 26 Apr 2023 05:07:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1682500064; 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=wl7FQJsNN76Vz4RdIelxp0LbGzYVpv9nvfw6HVwAW6Y=; b=QiVeCmm/M+fAkA61xIy31V8ojU6aFP/Mp1z8Y+njEID3gBdTBUl8P4vqMPioIr48DdWno+ IDoo16TB/sa7+FBrpvHnUzI0b3i6z0kNE7/0ttX//TcxGTM11JTFVJwj9YcuJAj2kWnWGM 8lEu5fgI/zAlzOJ0NzSR8n8AwTSLWKc= 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-216-3EX2yvqHMzKB3JArIUHX_A-1; Wed, 26 Apr 2023 05:07:40 -0400 X-MC-Unique: 3EX2yvqHMzKB3JArIUHX_A-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7E3DE101A531; Wed, 26 Apr 2023 09:07:40 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.88]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 284072027043; Wed, 26 Apr 2023 09:07:37 +0000 (UTC) Date: Wed, 26 Apr 2023 10:07:34 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Juan Quintela Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Paolo Bonzini , Thomas Huth , John Snow , Li Zhijian , Stefan Hajnoczi , Zhang Chen , Laurent Vivier Subject: Re: [PATCH v2 2/6] tests/qtests: remove migration test iterations config Message-ID: References: <20230421171411.566300-1-berrange@redhat.com> <20230421171411.566300-3-berrange@redhat.com> <87r0scgats.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87r0scgats.fsf@secure.mitica> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 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: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.171, 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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 Fri, Apr 21, 2023 at 11:54:55PM +0200, Juan Quintela wrote: > Daniel P. Berrangé wrote: > > The 'unsigned int interations' config for migration is somewhat > > overkill. Most tests don't set it, and a value of '0' is treated > > as equivalent to '1'. The only test that does set it, xbzrle, > > used a value of '2'. > > > > This setting, however, only relates to the migration iterations > > that take place prior to allowing convergence. IOW, on top of > > this iteration count, there is always at least 1 further migration > > iteration done to deal with pages that are dirtied during the > > previous iteration(s). > > > > IOW, even with iterations==1, the xbzrle test will be running for > > a minimum of 2 iterations. With this in mind we can simplify the > > code and just get rid of the special case. > > Perhaps the old code was already wrong, but we need at least three > iterations for the xbzrle test: > - 1st iteration: xbzrle is not used, nothing is on cache. Are you sure about this ? I see ram_save_page() calling save_xbzrle_page() and unless I'm mis-understanding the code, it doesn't appear to skip anything on the 1st iteration. IIUC save_xbzrle_page will add pages into the cache on the first iteration, so the second iteration will get cache hits > - 2nd iteration: pages are put into cache, no xbzrle is used because > there is no previous page. > - 3rd iteration: We really use xbzrle now against the copy of the > previous iterations. > > And yes, this should be commented somewhere. 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 :|