System Monitor Showing Incorrect Number of CPUs – Fix CPU Info


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.

Best Answer

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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