RE: [Newbie question] Why usage of CPU inside VM and outside VM is different

[Gregory Esnaud <Gregory.ESNAUD@exfo.com>]

Paolo,

In instantiated a VM to try idel=poll.

Before modify kernel parameters, I would like to check current config... sadely nothing at all talk about idle: 

root@imsprobe0:/home/adm_astellia# cat /proc/cmdline
ro root=/dev/mapper/rhel-root rd_NO_LUKS LANG=en_US.UTF-8 rd_LVM_LV=rhel/root rd_NO_MD SYSFONT=latarcyrheb-sun16  KEYBOARDTYPE=pc KEYTABLE=us crashkernel=129M@48M rhgb quiet rd_NO_DM rhgb quiet console=ttyS0
root@imsprobe0:/home/adm_astellia# sysctl -a|grep -i idle
kernel.sched_domain.cpu0.domain0.idle_idx = 1
kernel.sched_domain.cpu0.domain0.newidle_idx = 0
kernel.sched_domain.cpu1.domain0.idle_idx = 1
kernel.sched_domain.cpu1.domain0.newidle_idx = 0
kernel.sched_domain.cpu2.domain0.idle_idx = 1
kernel.sched_domain.cpu2.domain0.newidle_idx = 0
kernel.sched_domain.cpu3.domain0.idle_idx = 1
kernel.sched_domain.cpu3.domain0.newidle_idx = 0
kernel.sched_domain.cpu4.domain0.idle_idx = 1
kernel.sched_domain.cpu4.domain0.newidle_idx = 0
kernel.sched_domain.cpu5.domain0.idle_idx = 1
kernel.sched_domain.cpu5.domain0.newidle_idx = 0
kernel.sched_domain.cpu6.domain0.idle_idx = 1
kernel.sched_domain.cpu6.domain0.newidle_idx = 0
net.ipv4.tcp_slow_start_after_idle = 1


Cheers,


-----Message d'origine-----
De : kvm-owner@vger.kernel.org <kvm-owner@vger.kernel.org> De la part de Gregory Esnaud
Envoyé : mardi 7 janvier 2020 18:38
À : Paolo Bonzini <pbonzini@redhat.com>; kvm@vger.kernel.org
Objet : RE: [Newbie question] Why usage of CPU inside VM and outside VM is different

> That's a possibility.  And if it's correct, your provider is certainly 
> correct in complaining. :)
Yes, but as a cloud provider he should provide us prerequisites on VM config 😉.

I will give it a try!

Thanks!

-----Message d'origine-----
De : Paolo Bonzini <pbonzini@redhat.com> Envoyé : mardi 7 janvier 2020 18:36 À : Gregory Esnaud <Gregory.ESNAUD@exfo.com>; kvm@vger.kernel.org Objet : Re: [Newbie question] Why usage of CPU inside VM and outside VM is different

On 07/01/20 18:32, Gregory Esnaud wrote:
> Hi Paolo,
> 
> Thanks for your quick answer.
> 
> Are you using only 2 CPUs at 100%, or are you using 9 CPUs at a total of 200%? 
> 
> Inside the VM, a top command show that we are using 2 CPU @ 100%: 
> https://framadrop.org/r/gNf3erJVf6#t2HLIpzPHGtxHzHeLrnGGjsRSZZpmv9HPVZ
> t/LIIP8s= From the hypervisor (ie, *outside* the vm), a top command 
> show that the VM consuming 9 cpu:
> https://framadrop.org/r/-FmrBhMGX5#q/6aZ8Fq2Mnuzz3+6F/pa83U+jzPox1hd98
> 4tw7DkuA=
> 
> So, if I'm understanding you correctly, an parameter of kernel of our VM is idel=poll that we should change?
> 

That's a possibility.  And if it's correct, your provider is certainly correct in complaining. :)

Paolo