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 45B7BC433F5 for ; Fri, 25 Mar 2022 11:31:14 +0000 (UTC) Received: from localhost ([::1]:36086 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nXi9w-00089B-BP for qemu-devel@archiver.kernel.org; Fri, 25 Mar 2022 07:31:12 -0400 Received: from eggs.gnu.org ([209.51.188.92]:41868) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nXi8G-0007SD-FK for qemu-devel@nongnu.org; Fri, 25 Mar 2022 07:29:28 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:43932) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nXi8C-0007L6-8q for qemu-devel@nongnu.org; Fri, 25 Mar 2022 07:29:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648207761; 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=2MOKwvhZmljYFBFp85lKVWNHlctKtlgwwM9nCbkG4VY=; b=YIRdLDl4aKIwoB0hI2bOBGxg/aWeevhVUj66+glFrO5DJDCExvKUs1sjQk1UtpannFGWJi rU0+1J4FRcZm4nLiTWXHcOu5AsS6odvyrgMXc/kpRV8km/RDwxTBL56WLyO4ljj/PMKsM3 5bthyX5HbiZuWGMlfxWBs/xGWKfLsMY= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-210-m8FP-z0kOxOcdpYRB9_XcA-1; Fri, 25 Mar 2022 07:29:18 -0400 X-MC-Unique: m8FP-z0kOxOcdpYRB9_XcA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id ED65D1C05151; Fri, 25 Mar 2022 11:29:17 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.72]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 712252166B2D; Fri, 25 Mar 2022 11:29:13 +0000 (UTC) Date: Fri, 25 Mar 2022 11:29:11 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Claudio Fontana Subject: Re: [libvirt RFC] virFile: new VIR_FILE_WRAPPER_BIG_PIPE to improve performance Message-ID: References: <34eb53b5-78f7-3814-b71e-aa7ac59f9d25@suse.de> <2d1248d4-ebdf-43f9-e4a7-95f586aade8e@suse.de> <7c641d9d-fffa-e21b-7ae2-12ad35c0c238@suse.de> <35da2366-99e4-7680-a1c5-46aff83d747c@suse.de> <737974fa-905c-d171-05b0-ec4df42bc762@suse.de> MIME-Version: 1.0 In-Reply-To: <737974fa-905c-d171-05b0-ec4df42bc762@suse.de> User-Agent: Mutt/2.1.5 (2021-12-30) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@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=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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?= Cc: libvir-list@redhat.com, andrea.righi@canonical.com, Jiri Denemark , "Dr. David Alan Gilbert" , qemu-devel Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Mar 18, 2022 at 02:34:29PM +0100, Claudio Fontana wrote: > On 3/17/22 4:03 PM, Dr. David Alan Gilbert wrote: > > * Claudio Fontana (cfontana@suse.de) wrote: > >> On 3/17/22 2:41 PM, Claudio Fontana wrote: > >>> On 3/17/22 11:25 AM, Daniel P. Berrangé wrote: > >>>> On Thu, Mar 17, 2022 at 11:12:11AM +0100, Claudio Fontana wrote: > >>>>> On 3/16/22 1:17 PM, Claudio Fontana wrote: > >>>>>> On 3/14/22 6:48 PM, Daniel P. Berrangé wrote: > >>>>>>> On Mon, Mar 14, 2022 at 06:38:31PM +0100, Claudio Fontana wrote: > >>>>>>>> On 3/14/22 6:17 PM, Daniel P. Berrangé wrote: > >>>>>>>>> On Sat, Mar 12, 2022 at 05:30:01PM +0100, Claudio Fontana wrote: > >>>>>>>>>> the first user is the qemu driver, > >>>>>>>>>> > >>>>>>>>>> virsh save/resume would slow to a crawl with a default pipe size (64k). > >>>>>>>>>> > >>>>>>>>>> This improves the situation by 400%. > >>>>>>>>>> > >>>>>>>>>> Going through io_helper still seems to incur in some penalty (~15%-ish) > >>>>>>>>>> compared with direct qemu migration to a nc socket to a file. > >>>>>>>>>> > >>>>>>>>>> Signed-off-by: Claudio Fontana > >>>>>>>>>> --- > >>>>>>>>>> src/qemu/qemu_driver.c | 6 +++--- > >>>>>>>>>> src/qemu/qemu_saveimage.c | 11 ++++++----- > >>>>>>>>>> src/util/virfile.c | 12 ++++++++++++ > >>>>>>>>>> src/util/virfile.h | 1 + > >>>>>>>>>> 4 files changed, 22 insertions(+), 8 deletions(-) > >>>>>>>>>> > >>>>>>>>>> Hello, I initially thought this to be a qemu performance issue, > >>>>>>>>>> so you can find the discussion about this in qemu-devel: > >>>>>>>>>> > >>>>>>>>>> "Re: bad virsh save /dev/null performance (600 MiB/s max)" > >>>>>>>>>> > >>>>>>>>>> https://lists.gnu.org/archive/html/qemu-devel/2022-03/msg03142.html > >>>> > >>>> > >>>>> Current results show these experimental averages maximum throughput > >>>>> migrating to /dev/null per each FdWrapper Pipe Size (as per QEMU QMP > >>>>> "query-migrate", tests repeated 5 times for each). > >>>>> VM Size is 60G, most of the memory effectively touched before migration, > >>>>> through user application allocating and touching all memory with > >>>>> pseudorandom data. > >>>>> > >>>>> 64K: 5200 Mbps (current situation) > >>>>> 128K: 5800 Mbps > >>>>> 256K: 20900 Mbps > >>>>> 512K: 21600 Mbps > >>>>> 1M: 22800 Mbps > >>>>> 2M: 22800 Mbps > >>>>> 4M: 22400 Mbps > >>>>> 8M: 22500 Mbps > >>>>> 16M: 22800 Mbps > >>>>> 32M: 22900 Mbps > >>>>> 64M: 22900 Mbps > >>>>> 128M: 22800 Mbps > >>>>> > >>>>> This above is the throughput out of patched libvirt with multiple Pipe Sizes for the FDWrapper. > >>>> > >>>> Ok, its bouncing around with noise after 1 MB. So I'd suggest that > >>>> libvirt attempt to raise the pipe limit to 1 MB by default, but > >>>> not try to go higher. > >>>> > >>>>> As for the theoretical limit for the libvirt architecture, > >>>>> I ran a qemu migration directly issuing the appropriate QMP > >>>>> commands, setting the same migration parameters as per libvirt, > >>>>> and then migrating to a socket netcatted to /dev/null via > >>>>> {"execute": "migrate", "arguments": { "uri", "unix:///tmp/netcat.sock" } } : > >>>>> > >>>>> QMP: 37000 Mbps > >>>> > >>>>> So although the Pipe size improves things (in particular the > >>>>> large jump is for the 256K size, although 1M seems a very good value), > >>>>> there is still a second bottleneck in there somewhere that > >>>>> accounts for a loss of ~14200 Mbps in throughput. > >> > >> > >> Interesting addition: I tested quickly on a system with faster cpus and larger VM sizes, up to 200GB, > >> and the difference in throughput libvirt vs qemu is basically the same ~14500 Mbps. > >> > >> ~50000 mbps qemu to netcat socket to /dev/null > >> ~35500 mbps virsh save to /dev/null > >> > >> Seems it is not proportional to cpu speed by the looks of it (not a totally fair comparison because the VM sizes are different). > > > > It might be closer to RAM or cache bandwidth limited though; for an extra copy. > > I was thinking about sendfile(2) in iohelper, but that probably > can't work as the input fd is a socket, I am getting EINVAL. Yep, sendfile() requires the input to be a mmapable FD, and the output to be a socket. Try splice() instead which merely requires 1 end to be a pipe, and the other end can be any FD afaik. 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 :|