[pve-devel] intel pstate: wrong cpu frequency with performance governor

[Alexandre DERUMIER]

Ok,
I have test the patched kernel,

and I still have the same behavior, the frequency still go up and down.
(But it's not stuck anymore, like the bug I have see last week)

I think this is the normal behavior of pstate, as they are a lower limit.

But for virtualisation, I think it's really bad to have changing frequency. (clock problem for example).

Also for corosync, that mean that a loaded node will have faster frequency, and non-loaded node low frequency.
This can give us retransmit, because low frequency take more time to get the corosync message than the fastest node
https://www.hastexo.com/resources/hints-and-kinks/whats-totem-retransmit-list-all-about-corosync/


result:

without any load:

root at kvm1:/etc/pve# cat /proc/cpuinfo |grep MHz
cpu MHz		: 2025.292
cpu MHz		: 1520.816
cpu MHz		: 3261.175
cpu MHz		: 1875.742
cpu MHz		: 2923.445
cpu MHz		: 1935.078
cpu MHz		: 2860.597
cpu MHz		: 1671.820
cpu MHz		: 1200.039
cpu MHz		: 1653.656
cpu MHz		: 1602.433
cpu MHz		: 1935.320
cpu MHz		: 2042.972
cpu MHz		: 1359.761
cpu MHz		: 3460.253
cpu MHz		: 1200.039
cpu MHz		: 2163.097
cpu MHz		: 1710.328
cpu MHz		: 2249.316
cpu MHz		: 1199.675
cpu MHz		: 2473.945
cpu MHz		: 1731.398
cpu MHz		: 2541.273
cpu MHz		: 1658.863
cpu MHz		: 2528.800
cpu MHz		: 1680.660
cpu MHz		: 1922.847
cpu MHz		: 1369.570
cpu MHz		: 1940.890
cpu MHz		: 1526.507
cpu MHz		: 1952.878
cpu MHz		: 1452.761
cpu MHz		: 1788.675
cpu MHz		: 2137.910
cpu MHz		: 1942.828
cpu MHz		: 1707.664
cpu MHz		: 1438.957
cpu MHz		: 1642.757
cpu MHz		: 1561.382
cpu MHz		: 2104.730

running cpu benchmark:

root at kvm1:/etc/pve# cat /proc/cpuinfo |grep MHz
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902
cpu MHz		: 3199.902

----- Mail original -----
De: "aderumier" <aderumier at odiso.com>
À: "pve-devel" <pve-devel at pve.proxmox.com>
Envoyé: Lundi 19 Septembre 2016 10:08:45
Objet: Re: [pve-devel] intel pstate: wrong cpu frequency with performance governor

>>And it's being changed based on cpu load, like actual governor is ondemand. 

>From what I read, the intel pstate "performance", have a range min_freq / max_freq. 

So it seem to be different than cpufreq "performance", which is "max performance" 


(min_freq can be change manually through sysfs, but I don't think they are a kernel option to fix to max at boot) 



I'm currently compiling the kernel with patches from Stefan, I'll make a report this afternoon. 




----- Mail original ----- 
De: "Dmitry Petuhov" <mityapetuhov at gmail.com> 
À: "pve-devel" <pve-devel at pve.proxmox.com> 
Envoyé: Lundi 19 Septembre 2016 09:47:21 
Objet: Re: [pve-devel] intel pstate: wrong cpu frequency with performance governor 

19.09.2016 01:29, Alexandre DERUMIER wrote: 
> Hi, 
> 
> I have add some strange behaviour of some host last week, (cpu performance degrading) 
> 
> 
> and I have found than 3 hosts of my 15 host cluster have wrong cpu frequency. 
> 
> All nodes are dell r630, with xeon v3 3,1ghz. (all with last bios/microcode updates , last proxmox kernel) 
> 
> On the 3 hosts, the frequency was stuck to 800mhz instead 3,1ghz. (note that on other host, the frequency was not stable, up and down between 3,09 && 3,2ghz....) 
> 
> Cpu governor is correctly set to max performance in bios + linux. 
> 
> 
> It seem to be a problem with intel pstate driver. 
> 
> 
> I have disabled it with intel_pstate=disable in grub, (also can be disable with CONFIG_X86_INTEL_PSTATE=n) 
> and not frequency is super stable at 3,1ghz 
> 
> 
> Has somebody already seen this on xeon v3 ? 
Can confirm that on SandyBridge: 
model name : Intel(R) Xeon(R) CPU E5-2665 0 @ 2.40GHz 
root at msv-spb-pve01:/usr/share/perl5/PVE/Storage# cat 
/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq 
1199906 

And it's being changed based on cpu load, like actual governor is ondemand. 

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