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Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 16:33
by doynton
I have a macbook with i5 3210M processor with 2 physical cores
http://ark.intel.com/products/67355/Int ... 0-GHz-rPGA
VirtualBox gives me that message "More virtual CPUs are assigned to the virtual machine than the number of physical CPUs on the host system (
4)" if I try to assign more than 4 virtual CPUs. According to this support ticket if I understand it correctly it should be 2 - the number of
physical cores https://www.virtualbox.org/ticket/12480.
I am using VirtualBox version 4.3.22 released yesterday.
- Screen Shot.jpg (31.78 KiB) Viewed 12532 times
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 16:56
by loukingjr
You should normally only assign half the number of cores on your host. In your case, one CPU.
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 19:03
by doynton
loukingjr wrote:You should normally only assign half the number of cores on your host. In your case, one CPU.
I have only got one assigned. I tried 2 and 3 but the guest was slower.
The question is not how many to assign - it is whether VirtualBox is misreading the number present. It says 4 and as far as I know it should be 2 as my CPU has 2 cores.
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 19:29
by ChipMcK
The maximum number of potential CPUs appears to eight (8).
The machine you have is installed with two (2) CPUs, within the potential of eight (8).
Make sense?
( Check the slider for Monitor Count on the Display tab )
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 19:46
by doynton
ChipMcK wrote:The maximum number of potential CPUs appears to eight (8).
The machine you have is installed with two (2) CPUs, within the potential of eight (8).
Make sense?
( Check the slider for Monitor Count on the Display tab )
No - it doesn't make sense, sorry. My host is a Macbook Pro with
one i5-3210M processor (which has 2 cores). VirtualBox is showing it has
4 if you see the picture above.
I checked the Monitor Count on the Display tab and have one.
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 19:53
by ChipMcK
The slider for Monitor Count shows maximum of eight (8).
The slider for CPUs shows maximum of eight (8).
Or we caught in the Threads vs CPUs debate ?
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 20:24
by doynton
Both CPU and Monitor count have a maximum of 8. I'm unclear from the documentation what CPU has to do with maximum monitor count though - according to here
https://www.virtualbox.org/manual/ch03.html it is always 8.
Maybe it is threads vs cores debate but from my reading of the link in my first post there shouldn't be a debate. What is important is the number of physical cores of which I have 2. VirtualBox indicates 4.
Am I wrong and it is the number of threads not the number of physical cores?
Code: Select all
adams-mbp:~ adam$ vboxmanage list hostinfo
Host Information:
Host time: 2015-02-14T18:11:36.868000000Z
Processor online count: 4
Processor count: 4
Processor online core count: 4
Processor core count: 2
Processor#0 speed: 2500 MHz
Processor#0 description: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
Processor#1 speed: 2500 MHz
Processor#1 description: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
Processor#2 speed: 2500 MHz
Processor#2 description: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
Processor#3 speed: 2500 MHz
Processor#3 description: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
Memory size: 8192 MByte
Memory available: 1173 MByte
Operating system: Darwin
Operating system version: 14.1.0
adams-mbp:~ adam$
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 20:42
by ChipMcK
As an example: showing that the sliders show maximum values, while what you have installed is different.
Sorry for the confusion.
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 20:47
by loukingjr
The graph in VirtualBox is misleading. The log also calls cores and threads different things in different places. It's been that way for years now.
At any rate, your CPU does have 2 Cores and 4 Threads. VirtualBox indicates you can run up to 8 virtual CPUs although that's not really true. Why they don't change that I have no idea. I have all 4 core CPUs in my PCs and mine says 16 Virtual CPUs. The most I ever run for any guest is 2. A good rule of thumb is don't run more than n-1 virtual CPUs where n=physical cores.
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 21:07
by doynton
loukingjr wrote:A good rule of thumb is don't run more than n-1 virtual CPUs where n=physical cores.
That was my understanding. I'm not too concerned about the maximum. It is the fact that green (and green = good, right?) goes up to 4 and the warning message is ".... greater than the number of physical CPUs on the host system (4)"
It doesn't do it on Windows hosts. According to this thread the warning is tied to cores
My machine is i7-2600 (4 cores, 8 threads). ...... if I set it more than 4 VirtualBox will display a warning....
So it seems OSX host acts differently with respect to this warning compared to Windows host.
Re: Number of physical cores on host mis-identified?
Posted: 14. Feb 2015, 21:13
by loukingjr
I can set 8 CPUs before I get a warning. (end of the green section). If I set it to 9 or more, the warning says I have set more CPUs than I have physical cores.
Like I said, the warnings and settings could be less confusing.
