CPU frequency scaling / Windows VMs

[coder]

Hi,

I have a problem to understand the CPU frequency scaling in VMs.

On the server I have the following:

# cat /sys/devices/system/cpu/cpu4/cpufreq/scaling_governor
performance

# lscpu
Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
Address sizes:       40 bits physical, 48 bits virtual
CPU(s):              16
On-line CPU(s) list: 0-15
Thread(s) per core:  2
Core(s) per socket:  4
Socket(s):           2
NUMA node(s):        2
Vendor ID:           GenuineIntel
CPU family:          6
Model:               26
Model name:          Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
Stepping:            5
CPU MHz:             2029.822
CPU max MHz:         1597.0000
CPU min MHz:         1596.0000
BogoMIPS:            3192.10
Virtualization:      VT-x
L1d cache:           32K
L1i cache:           32K
L2 cache:            256K
L3 cache:            8192K
NUMA node0 CPU(s):   0,2,4,6,8,10,12,14
NUMA node1 CPU(s):   1,3,5,7,9,11,13,15
Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 popcnt lahf_lm pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid dtherm ida flush_l1d

Look at the field: CPU max MHz: 1597.0000

I would expect to see 2.93 GHz per CPU in a VM (all Windows). But I see the following:

Maximal CPU Speed: 1.60 GHz

I do suspect a BIOS setting or something like that. But I cannot be sure - Do have some experience here?
On another server of a difference site, the field of "CPU max MHz" looks like this:

root@SRV01:~# lscpu
Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
Address sizes:       40 bits physical, 48 bits virtual
CPU(s):              16
On-line CPU(s) list: 0-15
Thread(s) per core:  2
Core(s) per socket:  4
Socket(s):           2
NUMA node(s):        2
Vendor ID:           GenuineIntel
CPU family:          6
Model:               26
Model name:          Intel(R) Xeon(R) CPU           X5560  @ 2.80GHz
Stepping:            5
CPU MHz:             1863.840
CPU max MHz:         2794.0000
CPU min MHz:         1596.0000
BogoMIPS:            5586.42
Virtualization:      VT-x
L1d cache:           32K
L1i cache:           32K
L2 cache:            256K
L3 cache:            8192K
NUMA node0 CPU(s):   0,2,4,6,8,10,12,14
NUMA node1 CPU(s):   1,3,5,7,9,11,13,15
Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cm                                                        ov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx rdtscp lm c                                                        onstant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aper                                                        fmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse                                                        4_2 popcnt lahf_lm pti tpr_shadow vnmi flexpriority ept vpid dtherm ida

Best Regards,
coder

 

[Stefan_R]

I don't know why, but in your first example your CPU is severely underreporting it's stock maximum frequence. However, as indicated by the "CPU MHz:" line, it is actually using it's correct clock speed.

It always reports it's stock frequency to the VM, so that is fine too. AFAIK there is currently no reliable way to get the actual frequency inside a VM.

TL;DR: I don't know why it's reporting that, but it shouldn't affect anything performance wise.

 

[coder]

Thank You for your anwer.

We found the issue:



Today, we exchange the power supplies!

Now, on the systems we have the right values:

Model name:          Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
Stepping:            5
CPU MHz:             2447.390
CPU max MHz:         2927.0000
CPU min MHz:         1596.0000
BogoMIPS:            5852.17