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Tue, 10 Nov 2020 14:16:49 +0000 (GMT) Received: from [9.145.70.110] (unknown [9.145.70.110]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 10 Nov 2020 14:16:49 +0000 (GMT) Subject: Re: [PATCH 1/1] virtio-blk-ccw: tweak the default for num_queues To: Halil Pasic , Cornelia Huck References: <20201109154831.20779-1-pasic@linux.ibm.com> <20201109170616.6875f610.cohuck@redhat.com> <20201109195303.459f6fba.pasic@linux.ibm.com> From: Michael Mueller Organization: IBM Message-ID: <4a3d24e0-399f-f509-9a5c-c66c57b2d28a@linux.ibm.com> Date: Tue, 10 Nov 2020 15:16:49 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <20201109195303.459f6fba.pasic@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312, 18.0.737 definitions=2020-11-10_05:2020-11-10, 2020-11-10 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 impostorscore=0 mlxscore=0 phishscore=0 clxscore=1011 bulkscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 suspectscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011100096 Received-SPF: pass client-ip=148.163.158.5; envelope-from=mimu@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/10 09:16:55 X-ACL-Warn: Detected OS = Linux 3.x [generic] X-Spam_score_int: -19 X-Spam_score: -2.0 X-Spam_bar: -- X-Spam_report: (-2.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: mimu@linux.ibm.com Cc: Thomas Huth , "Michael S. Tsirkin" , David Hildenbrand , qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 09.11.20 19:53, Halil Pasic wrote: > On Mon, 9 Nov 2020 17:06:16 +0100 > Cornelia Huck wrote: > >>> @@ -20,6 +21,11 @@ static void virtio_ccw_blk_realize(VirtioCcwDevice *ccw_dev, Error **errp) >>> { >>> VirtIOBlkCcw *dev = VIRTIO_BLK_CCW(ccw_dev); >>> DeviceState *vdev = DEVICE(&dev->vdev); >>> + VirtIOBlkConf *conf = &dev->vdev.conf; >>> + >>> + if (conf->num_queues == VIRTIO_BLK_AUTO_NUM_QUEUES) { >>> + conf->num_queues = MIN(4, current_machine->smp.cpus); >>> + } >> >> I would like to have a comment explaining the numbers here, however. >> >> virtio-pci has a pretty good explanation (use 1:1 for vqs:vcpus if >> possible, apply some other capping). 4 seems to be a bit arbitrary >> without explanation, although I'm sure you did some measurements :) > > Frankly, I don't have any measurements yet. For the secure case, > I think Mimu has assessed the impact of multiqueue, hence adding Mimu to > the cc list. @Mimu can you help us out. > > Regarding the normal non-protected VMs I'm in a middle of producing some > measurement data. This was admittedly a bit rushed because of where we > are in the cycle. Sorry to disappoint you. I'm talking with the perf team tomorrow. They have done some measurements with multiqueue for PV guests and I asked for a comparison to non PV guests as well. Michael > > The number 4 was suggested by Christian, maybe Christian does have some > readily available measurement data for the normal VM case. @Christian: > can you help me out? > > Regards, > Halil > -- Mit freundlichen Grüßen / Kind regards Michael Müller IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Gregor Pillen Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294