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I'm currently running Ubuntu 14.04.2 Desktop.

The System Monitor tool is showing me 32 CPUs when I'm expecting 56. Should I be concerned?

Screenshot of System Monitor:

Screenshot of System Monitor

As you can see, it shows 32 CPUs.

Output of lscpu:

~$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                56
On-line CPU(s) list:   0-55
Thread(s) per core:    2
Core(s) per socket:    14
Socket(s):             2
NUMA node(s):          2
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 63
Stepping:              2
CPU MHz:               1337.882
BogoMIPS:              5189.07
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              35840K
NUMA node0 CPU(s):     0-13,28-41
NUMA node1 CPU(s):     14-27,42-55

As you can see, according to lscpu, I should have 56 CPUs.

htop is also showing me 56 CPUs.

Screenshot of htop

My machine is Dell's T7910 Precision tower. It has 2 Intel Xeon E5-2697 V3 processors, each having 14 cores and capable of 2 threads per core (as seen in the output of lscpu, and further confirmed in BIOs).

I recall seeing 56 cores under System Monitor when I launched it in the "try ubuntu" mode from the installation disk before installing Ubuntu.

  1. Is there something wrong with my system configuration?
  2. If there is (e.g., hardware failure), what can I do to verify?
  3. Also, I noticed that my System Monitor does not have a "System" tab.
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  • Its normal for system monitor to not show the system tab in Ubuntu 14.04. I don't know what version it was removed, though.
    – user371765
    Apr 26, 2015 at 6:58
  • @ethanbmnz Thanks for the quick reply. You are correct. The "System" tab is no longer available. Apr 26, 2015 at 7:01

1 Answer 1

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In Short

  1. Your system configuration is probably fine. Gnome-system-monitor is simply reporting the wrong number.
  2. No need to worry.
  3. As already mentioned in a comment above, the “System” tab is gone in Ubuntu 14.04.

In More Detail

You have hit a hard upper CPU number limit that is set in libgtop (a library which is used by gnome-system-monitor). Quoting from the code:

/* Nobody should really be using more than 4 processors.
   Yes we are :)
   Nobody should really be using more than 32 processors.
*/
#define GLIBTOP_NCPU        32

This limit has been increased to 1024 in more recent libgtop versions than the one shipped with Ubuntu 14.04.

Aside from being annoying to not see a good bunch of CPUs in gnome-system-monitor, this bug should be harmless. You might be able to fix it by installing a more recent version of libgtop. Alternatively, you could upgrade to a newer Ubuntu version. The question is whether the gnome-system-monitor annoyance is worth the hassle of upgrading or trying a more recent version of libgtop.

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  • 1
    Thank you! My htop was showing the correct number but gnome-system-monitor was not. Hence my worry that the OS was "detecting" the CPUs, but not "using" them. It is good to know that this is not a problem. But curiously, I swear I saw all 56 CPUs in the System Monitor when I "tried ubuntu" from the live CD. Apr 26, 2015 at 8:24
  • And the live CD was the same Ubuntu version that you have running locally now? If so and if there were really 56 CPUs shown, then that’d be a mystery to me. I wouldn’t expect the live CD to run a different version of libgtop than the installed version of Ubuntu.
    – Chriki
    Apr 26, 2015 at 9:31
  • In trying to install Ubuntu I burned several copies on DVD and even one on a flash drive (I had a lot of trouble installing alongside a preinstalled Windows 8.1). I think the one that I saw the 56 CPUs was 14.10, not 14.04, even though eventually I installed 14.04. Perhaps 14.10 had disabled the limit. Apr 26, 2015 at 9:36
  • 2
    Indeed, Ubuntu 14.10 uses libgtop in version 2.30.0 which already has the limit of 1024 CPUs.
    – Chriki
    Apr 26, 2015 at 9:42
  • @Chriki just curious, does the newer version add another "Yes we are!" to the comment? :) Nvm. It doesn't. :(
    – muru
    Apr 26, 2015 at 10:51

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