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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id r188-20020a1c2bc5000000b00387c81c32e7sm5961322wmr.8.2022.03.09.10.39.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Mar 2022 10:39:46 -0800 (PST) Date: Wed, 9 Mar 2022 18:39:44 +0000 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: bad virsh save /dev/null performance (600 MiB/s max) Message-ID: References: <5f318297-51c0-366b-758b-733ba27684ba@suse.de> <5b3d17d2-f07f-8cb1-54ff-6a517dc4eaef@suse.de> <51b486fc-2c71-e1c6-6412-d462234d67fb@suse.de> <700779ea-4274-7872-6022-d32457a00160@suse.de> <47786b29-b1a2-1f6a-568d-b61398e0f641@suse.de> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.1.5 (2021-12-30) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@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: , Cc: Jim Fehlig , Juan Quintela , Claudio Fontana , qemu-devel Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Daniel P. Berrangé (berrange@redhat.com) wrote: > On Wed, Mar 09, 2022 at 07:27:12PM +0100, Claudio Fontana wrote: > > > > One difference I could see looking at the qmp commands issued by libvirt in the "virsh save" case, > > is "detach:true" in the migration command (which seems to have no effect in qemu), > > That is a bug in libvirt - it should not be setting that in QMP. > > To quote the QAPI spec for 'migrate' > > # @detach: this argument exists only for compatibility reasons and > # is ignored by QEMU > > > > > > > > and maybe more interestingly this stuff about the "fd": > > > > > > 2022-03-09 17:29:34.247+0000: 20390: info : qemuMonitorSend:995 : QEMU_MONITOR_SEND_MSG: mon=0x7faa9003ebf0 msg={"execute":"getfd","arguments":{"fdname":"migrate"},"id":"libvirt-390"}^M > > fd=34 > > 2022-03-09 17:29:34.247+0000: 20387: info : qemuMonitorIOWrite:452 : QEMU_MONITOR_IO_WRITE: mon=0x7faa9003ebf0 buf={"execute":"getfd","arguments":{"fdname":"migrate"},"id":"libvirt-390"}^M > > len=73 ret=73 errno=0 > > 2022-03-09 17:29:34.247+0000: 20387: info : qemuMonitorIOWrite:457 : QEMU_MONITOR_IO_SEND_FD: mon=0x7faa9003ebf0 fd=34 ret=73 errno=0 > > 2022-03-09 17:29:34.248+0000: 20387: info : qemuMonitorJSONIOProcessLine:240 : QEMU_MONITOR_RECV_REPLY: mon=0x7faa9003ebf0 reply={"return": {}, "id": "libvirt-390"} > > 2022-03-09 17:29:34.249+0000: 20390: info : qemuMonitorSend:995 : QEMU_MONITOR_SEND_MSG: mon=0x7faa9003ebf0 msg={"execute":"migrate","arguments":{"detach":true,"blk":false,"inc":false,"uri":"fd:migrate"},"id":"libvirt-391"}^M > > fd=-1 > > 2022-03-09 17:29:34.249+0000: 20387: info : qemuMonitorIOWrite:452 : QEMU_MONITOR_IO_WRITE: mon=0x7faa9003ebf0 buf={"execute":"migrate","arguments":{"detach":true,"blk":false,"inc":false,"uri":"fd:migrate"},"id":"libvirt-391"}^M > > len=113 ret=113 errno=0 > > > > > > in qemu I am currently looking at the code in migration/socket.c > > vs the code in migration/fd.c , wonder if the difference would > > stem from there.. > > When saving to a file, libvirt passes in a pre-opened FD for > QEU to use. IIRC this should always be a pipe FD connected to > libvirt's iohelper program, sometimes indirectly via a compression > program. In which case, what is a simple 'top' showing on the system? Dave > 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 :| > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK