Open Stack

On Mon, 2023-08-21 at 15:06 +0200, Jan Wasilewski wrote:
> Hi,
> 
> Let me add a few points. Lastly, I decided to conduct a couple of tests
> with the newer OpenStack platform - Zed (built by the kolla-ansible
> project). This platform serves Ubuntu 22.04 LTS on top of my compute nodes.
> The results were surprising, particularly because I was able to achieve the
> desired outcomes.
> 
> My compute node was equipped with 2 SSDs and 2 NVMe disks. As a preliminary
> step, I used SSD drives for testing. The fio test yielded a result of
> approximately 90k IOPS for the local SSD drive [1], employing
> IvyBridge-IBRS as the cpu_model parameter. When I transitioned to
> Cascadelake-Server, I managed to exceed 100k IOPS [2]. Interestingly, when
> I conducted an identical test with NVMe drives, the performance was only
> slightly above 90k IOPS [3]. This suggests that NVMe drives are marginally
> slower than SSD drives for local storage when used by VMs.
> 
> For the final test, I executed the fio test on the NVMe mounting point,
> achieving around 140k IOPS [4].
> 
> In summary, it appears that the choice of Ubuntu version as the base for
> compute nodes has a significant impact on performance (Ubuntu 20.04 LTS vs.
> Ubuntu 22.04 LTS). In my opinion, a kernel parameter seems to be
> responsible for constraining the performance within the VM (more precisely,
> the "drive file" serving as local storage for the VM). However, I'm
> uncertain about which specific parameter(s) are at play. I intend to delve
> deeper into this matter, but I'm open to any suggestions you may have.
thanks for reporting your observation.
this may or may not be kernel related if you are using diffent version fo QEMU between
each ubuntu release.
if its the same version then this may indeed be related to kernel change but it may not
be with parmater. rather it could be with change to the filesystem that may have improved
performance for vm workloads. it could also be related to enhancements with some of the
kernel mitigation that are used or a number of other factors. 20.04 to 22.04 is a large
leap and there are alot of changes even if you are deploying the same version of openstack
using package form the cloud archive on 20.04,

if you want to get the highest possible performance in the guest instead of setting
a virutral cpu model you should set 
[libvirt]
cpu_mode=host-passthrough

instead of 
[libvirt]
cpu_mode=custom
cpu_models=Cascadelake-Server

the down side to using host-passthrough is you will only be able to live migrate to servers
with the exact same model of cpu. if all your cpus are the same or you can sub devied
your cloud into sets of host with the same cpu sku i.e. via host aggrates and filters/traits 
then that's not really an issue.


if you do find a kernel parmater to acchive the same performacne on 20.04 please let us
know but i suspect its a combination of things that have change between both releases
rhater then a single thing.

> 
> /Jan Wasilewski
> *References:*
> *[1] fio results for IvyBridge and SSDs:
> https://paste.openstack.org/show/bUCoXBUbImd9JxplPBbv/
> <https://paste.openstack.org/show/bUCoXBUbImd9JxplPBbv/>*
> *[2] fio results for Cascadelake-Server and SSDs:
> https://paste.openstack.org/show/bWxDkM5ITcMTlFWe4GiZ/
> <https://paste.openstack.org/show/bWxDkM5ITcMTlFWe4GiZ/>*
> *[3] fio results for Cascadelake-Server and NVMe:
> https://paste.openstack.org/show/bbINpvkNZcJcY0KP0vPo/
> <https://paste.openstack.org/show/bbINpvkNZcJcY0KP0vPo/>*
> *[4] fio results for mounting point of NVMe:
> https://paste.openstack.org/show/bTchYOYY3zNpSLPfOpQl/
> <https://paste.openstack.org/show/bTchYOYY3zNpSLPfOpQl/>*
> 
> czw., 17 sie 2023 o 12:16 Jan Wasilewski <finarffin at gmail.com> napisał(a):
> 
> > Hi,
> > 
> > First and foremost, I want to express my heartfelt gratitude for all the
> > invaluable insights you've provided. I meticulously studied and conducted
> > numerous tests based on your inputs. While I've managed to implement
> > certain enhancements, I'd like to delve into those improvements in an
> > upcoming section. For now, let me address your queries.
> > 
> > Regarding the number of concurrent VMs operating on the OpenStack
> > hypervisor:
> > 
> >    - Presently, there is a sole VM running on this compute node,
> >    occasionally there might be two instances. The compute node remains largely
> >    underutilized, primarily earmarked for my performance assessments. It's
> >    equipped with a 24-core Intel(R) Xeon(R) Silver 4214 CPU @ 2.20GHz,
> >    alongside a MemTotal of 48988528 kB. Thus far, I haven't detected any red
> >    flags. Even during the execution of fio tests within my VMs, there is no
> >    discernible surge in load.
> > 
> > To @smooney: In relation to ide and virtio, I undertook a secondary test,
> > meticulously duplicating the attachment methodology, and the outcomes are
> > akin. Please refer to [1] and [2].
> > 
> > Nevertheless, as per your recommendation, I explored hw_pmu; however, the
> > outcomes remained consistent. Find the results with hw_pmu disabled in [3],
> > [4], and [5], and contrasting results with hw_pmu enabled in [6], [7], and
> > [8].
> > 
> > Nonetheless, I did experience a substantial performance escalation, albeit
> > solely for a manually attached disk—a comprehensive drive, not the disk
> > associated with the VM as a singular file [9]. The solitary alteration
> > involved configuring my cpu_model in nova.conf from IvyBridge to
> > Cascadelake-Server-noTSX. Even though I achieved approximately 110k iOPS
> > for the fully attached disk [10], the file-attached disk retained around
> > 19k iOPS [11], with comparable performance evident for the root disk [12].
> > The latter is also a solitary file, albeit located on a distinct drive of
> > the same model. For your perusal, I've appended all relevant dumpxml data
> > [13]. In summation, it seems that the cpu_model significantly influences
> > performance enhancement, though this effect is not replicated for a "file
> > disk." The query thus stands: how can we elevate performance for a file
> > disk?
> > 
> > Might you be willing to share the fio benchmark outcomes from your local
> > storage configuration? I'm curious to ascertain whether our results align,
> > or if there's a concealed optimization path I have yet to uncover. I
> > sincerely appreciate all the assistance you've extended thus far.
> > /Jan Wasilewski
> > 
> > *References:*
> > *[1] virtio connected via virsh attach-volume to Openstack instance(<80k
> > iOPS): https://paste.openstack.org/show/bHqZZWdAwWVYh1rHaIgC/
> > <https://paste.openstack.org/show/bHqZZWdAwWVYh1rHaIgC/>*
> > *[2] virtio connected via virsh attach-volume to Openstack instance
> > dumpxml: https://paste.openstack.org/show/bvEsKiwBd8lL4AUPSOxj/
> > <https://paste.openstack.org/show/bvEsKiwBd8lL4AUPSOxj/>*
> > *[3] hw_pmu: False: fio - root disk:
> > https://paste.openstack.org/show/bAZXQOUrkmVBsJ7yBEql/
> > <https://paste.openstack.org/show/bAZXQOUrkmVBsJ7yBEql/>*
> > *[4] hw_pmu: False: fio - attached nvme disk:
> > https://paste.openstack.org/show/bF1P0qsVG24duuY8F6HV/
> > <https://paste.openstack.org/show/bF1P0qsVG24duuY8F6HV/>*
> > *[5] hw_pmu: False: dumpxml:
> > https://paste.openstack.org/show/b8Yxf5DmPmAxxA070DL1/
> > <https://paste.openstack.org/show/b8Yxf5DmPmAxxA070DL1/>*
> > *[6] hw_pmu: True: fio - root disk:
> > https://paste.openstack.org/show/b7jJ7gR2e9VAAXm1e9PP/
> > <https://paste.openstack.org/show/b7jJ7gR2e9VAAXm1e9PP/>*
> > *[7] hw_pmu: True: fio - attached nvme disk(82,5k iOPS) :
> > https://paste.openstack.org/show/bCrdOnwxrJS6hENxTMK5/
> > <https://paste.openstack.org/show/bCrdOnwxrJS6hENxTMK5/>*
> > *[8] hw_pmu: True: dumpxml:
> > https://paste.openstack.org/show/b8Yxf5DmPmAxxA070DL1/
> > <https://paste.openstack.org/show/b8Yxf5DmPmAxxA070DL1/>*
> > *[9] Instruction how to add a "file disk" to kvm instance:
> > https://www.cyberciti.biz/faq/how-to-add-disk-image-to-kvm-virtual-machine-with-virsh-command/
> > <https://www.cyberciti.biz/faq/how-to-add-disk-image-to-kvm-virtual-machine-with-virsh-command/>*
> > *[10] cpu_model: Cascadelake-Server-noTSX fio - attached nvme disk(almost
> > 110k iOPS): https://paste.openstack.org/show/bdKQIgNIH0dy8PLhAIKq/
> > <https://paste.openstack.org/show/bdKQIgNIH0dy8PLhAIKq/>*
> > *[11] cpu_model: Cascadelake-Server-noTSX fio - "file disk":
> > https://paste.openstack.org/show/bjBmPBXi35jWdyJ1cjQt/
> > <https://paste.openstack.org/show/bjBmPBXi35jWdyJ1cjQt/>*
> > *[12] cpu_model: Cascadelake-Server-noTSX fio - root disk:
> > https://paste.openstack.org/show/br49T918vNU5NJXfXYGm/
> > <https://paste.openstack.org/show/br49T918vNU5NJXfXYGm/>*
> > *[13] cpu_model: Cascadelake-Server-noTSX dumpxml:
> > https://paste.openstack.org/show/bns2rWIHCHIWbrR9LUD0/
> > <https://paste.openstack.org/show/bns2rWIHCHIWbrR9LUD0/>*
> >