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Oh, thanks for that detailed explanation!
I was looking at metrics weighter for years and looked through code couple
of times but never got it properly configured. That is very helpful, thanks
a lot!

чт, 16 мар. 2023 г., 09:46 Sean Mooney <smooney at redhat.com>:

> On Thu, 2023-03-16 at 02:03 +0100, Dmitriy Rabotyagov wrote:
> > Eventually I don't fully understand reasons behind need of such service.
> >
> > As fighting with high load by migrating instances between computes is
> > fighting with consequences rather then with root cause, not saying that
> it
> > brings more negative effects then positive for experience of the
> end-users,
> > as you're just moving problem to another place affecting more workloads
> > with degraded performance.
> >
> > If you struggling from high load on a daily basis - then you have too
> high
> > cpu_allocation_ratio set for computes. As high load issues always come
> from
> > attempts to oversell too agressively.
> >
> > If you have workloads in the cloud that always utilize all CPUs
> available -
> > then you should consider having flavors and aggregates with cpu-pinning,
> > meaning providing physical CPUs for such workloads.
> >
> > Also don't forget, that it's worth setting more realistic numbers for
> > reserved resources on computes, because default 2gb of RAM is usually too
> > small.
> i tend to agree although there are some thing you can do in the nova
> schduler ot help
> e.g. prefering spreading over packing.
>
> for cpu load in particalar you can also enable the metric weigher
>
> i have not read this thread in detail altough skiming i see refrences to
> ceilometer.
> nova's metrics weigher has no depency on it.
> the metrics weigher
>
> https://github.com/openstack/nova/blob/master/nova/scheduler/weights/metrics.py
> is configured by adding weight_setting in the schduler config
>
> https://docs.openstack.org/nova/latest/configuration/config.html#metrics.weight_setting
>
>     [metrics]
>     weight_setting = name1=1.0, name2=-1.0
> and enabeling the monitors in the nova-comptue config
>
> https://docs.openstack.org/nova/latest/configuration/config.html#DEFAULT.compute_monitors
> [DEFAULT]
> compute_monitors = cpu.virt_driver
>
> ^ that is the only one we support
>
> the datafiles we report are set here
>
> https://github.com/openstack/nova/blob/master/nova/compute/monitors/cpu/virt_driver.py#L52-L101
>
> the more intersting values are
> "cpu.iowait.percent", "cpu.idle.percent" and "cpu.percent"
>
> we have a fairly large internal cloud that is used for dev and ci and as
> of about 12 to 18 months ago they
> have been using this to help balance the schduling fo instance as we have
> a mix of hyperviros skus
> and this help blance systme load.
>
>   [metrics]
>     weight_setting = cpu.iowait.percent=-1.0, cpu.percent=-1.0,
> cpu.idle.percent=1.0
>
> you want iowait and cpu.percent to be negitive since you want to avoid
> host with high iowait or high cpu utilsation.
> and you woudl want to prefer idle host if your intent is to blance load.
>
> iowait is actully included in cpu.percent and infact cpu.percent is
> basicaly cpu load - idel so
> [metrics]
>     weight_setting = cpu.percent=-1.0
> would have a simialreffect but you might want the extra granularity to
> weight iowait vs idle differntly
>
> so if you find the normal cpu/ram/disk weigher are not sufficent to blance
> based onload check out the
> metrics weigher and see it that helps. just be awere that collecting the
> cpu metrics and providing them
> to the schduelr will increase rabbitmq load a little since we perodicly
> have ot update those values for
> each compute. if you have a lot of compute that might be problematic. its
> one of the reasons we
> decided not to add more metrics like this.
>
>
>
> >
> >
> >
> > ср, 15 мар. 2023 г., 13:11 Nguyễn Hữu Khôi <nguyenhuukhoinw at gmail.com>:
> >
> > > Hello.
> > > I cannot use because missing cpu_util metric. I try to match it work
> but
> > > not yet. It need some code to make it work. It seem none care about
> balance
> > > reources on cloud.
> > >
> > > On Wed, Mar 15, 2023, 6:26 PM Thomas Goirand <zigo at debian.org> wrote:
> > >
> > > > On 12/11/22 01:59, Nguyễn Hữu Khôi wrote:
> > > > > Watcher is not good because It need cpu metric
> > > > > such as cpu load in Ceilometer which is removed so we cannot use
> it.
> > > >
> > > > Hi!
> > > >
> > > > What do you mean by "Ceilometer [is] removed"? It certainly isn't
> dead,
> > > > and it works well... If by that, you mean "ceilometer-api" is
> removed,
> > > > then yes, but then you can use gnocchi.
> > > >
> > > > Cheers,
> > > >
> > > > Thomas Goirand (zigo)
> > > >
> > > >
>
>
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