Linux check cpu cores

How to know number of cores of a system in Linux?

I wanted to find out how many cores my system has, so I searched the same question in Google. I got some commands such as the lscpu command. When I tried this command, it gave me the following result:

$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 4 On-line CPU(s) list: 0-3 Thread(s) per core: 1 Core(s) per socket: 4 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 23 Stepping: 10 CPU MHz: 1998.000 BogoMIPS: 5302.48 Virtualization: VT-x L1d cache: 32K L1i cache: 32K L2 cache: 2048K NUMA node0 CPU(s): 0-3 

Which of those indicates cores of a Linux system?

Is there any other command to tell the number of cores, or am I assuming it is completely wrong?

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@สมหวังแนวหน้า kind of a nitpick, but the the grep arg should be processor , not precessor , correct? . Thanks for the help!

12 Answers 12

To get a complete picture you need to look at the number of threads per core, cores per socket and sockets. If you multiply these numbers you will get the number of CPUs on your system.

CPUs = Threads per core X cores per socket X sockets

CPUs are what you see when you run htop (these do not equate to physical CPUs).

Here is an example from a desktop machine:

$ lscpu | grep -E '^Thread|^Core|^Socket|^CPU\(' CPU(s): 8 Thread(s) per core: 2 Core(s) per socket: 4 Socket(s): 1 

$ lscpu | grep -E '^Thread|^Core|^Socket|^CPU\(' CPU(s): 32 Thread(s) per core: 2 Core(s) per socket: 8 Socket(s): 2 

The output of nproc corresponds to the CPU count from lscpu . For the desktop machine above this should match the 8 CPU(s) reported by lscpu :

The output of /proc/cpuinfo should match this information, for example on the desktop system above we can see there are 8 processors (CPUs) and 4 cores (core id 0-3):

$ grep -E 'processor|core id' /proc/cpuinfo processor : 0 core id : 0 processor : 1 core id : 0 processor : 2 core id : 1 processor : 3 core id : 1 processor : 4 core id : 2 processor : 5 core id : 2 processor : 6 core id : 3 processor : 7 core id : 3 

The cpu cores reported by /proc/cpuinfo corresponds to the Core(s) per socket reported by lscpu . For the desktop machine above this should match the 4 Core(s) per socket reported by lscpu:

$ grep -m 1 'cpu cores' /proc/cpuinfo cpu cores : 4 

To specifically answer your question you tell how many cores you have by multiplying the number of cores you have per socket by the number of sockets you have.

Cores = Cores per socket X Sockets

For the example systems above the desktop has 4 cores:

$ echo "Cores = $(( $(lscpu | awk '/^Socket\(s\)/< print $2 >') * $(lscpu | awk '/^Core\(s\) per socket/< print $4 >') ))" Cores = 4 

$ echo "Cores = $(( $(lscpu | awk '/^Socket\(s\)/< print $2 >') * $(lscpu | awk '/^Core\(s\) per socket/< print $4 >') ))" Cores = 16 

Another useful utility is dmidecode which outputs per socket information. In the case of the server system listed above we expect to see 8 cores per socket and 16 threads per socket:

$ sudo dmidecode -t 4 | grep -E 'Socket Designation|Count' Socket Designation: CPU1 Core Count: 8 Thread Count: 16 Socket Designation: CPU2 Core Count: 8 Thread Count: 16 

The lscpu command has a number of useful options that you may like to check out, for example:

$ lscpu --all --extended $ lscpu --all --parse=CPU,SOCKET,CORE | grep -v '^#' 

See man lscpu for details.

• You need to be aware of sockets, cores and threads
• You need to be careful of the term CPU as it means different things in different contexts

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How to Get the Number of Processors/Cores in Linux

It is a no-brainer that the various Linux operating system distributions that provide irreplaceable performance prowess in a development or production environment will lose their performance identity in the absence of processors/cores.

These processors/cores are hardware entities of a computer system responsible for computing how fast the Linux operating system and its hosted programs complete user/system assigned tasks.

The evolution/innovation of various computer hardware infrastructures has led to the production of modern CPUs whose processors/cores embrace features like hyper-threading and multiple cores.

Importance of Knowing the Number of Processors/Cores in Linux

When working under an open-source operating system distribution like Linux, performance is everything. You need both the hardware and software components of your computing system to be at their best.

Therefore, knowing the number of processors/cores on the machine that powers your Linux operating system helps gauge how best your OS can perform under specific/customizable computing conditions.

For instance, you might be able to understand why multiple cores/hyper-threading CPUs have a speed and performance advantage over single-Core CPUs without hyper-threading.

1. Find Linux CPU Processors/Cores Using /proc/cpuinfo File

Whether on a remote Linux server or desktop Linux system, this method will query the /proc/cpuinfo file for lines matching the keyword processor via grep command which passes the processor keyword to a wc (word count) function that sums it up for display.

$ cat /proc/cpuinfo | grep processor | wc -l 4 

A more detailed output of the above file will look like the following:

2. Get Linux CPU Processors/Cores Using lscpu Command

To understand what lscpu command does, we first need to run it:

The lscpu command also highlights the CPU’s Architecture, op-mode(s), address sizes, thread(s) per core, core(s) per socket, family, model name, etc.

3. Check Linux CPU Processors/Cores Using top Command

Key in the command (top) on your Linux system and hit [Enter] on your keyboard. You should get a detailed output on what is going on with your processors/cores.

4. List Linux CPU Processors/Cores Using nproc Command

This approach is straightforward and will only output the available CPUs on your Linux system.

$ nproc --all 4 

An alternative approach to execute this command is as follows:

$ echo "Threads/core: $(nproc --all)"

5. List Linux CPU Processors/Cores Using getconf Command

This command is straightforward and can be executed in the following manner:

$ getconf _NPROCESSORS_ONLN 4 

An alternative approach to executing this command is as follows:

$ echo "Number of CPU/cores online at $HOSTNAME: $(getconf _NPROCESSORS_ONLN)"

6. Find Linux CPU Processors/Cores Using dmidecode Command

The dmidecodeis command is used to get the Linux system’s hardware related information such as Processor, RAM, BIOS detail, Memory, Serial numbers etc.

We can alternatively modify the execution of the above command to provide us with CPU details like version, core count, core enabled, and thread count.

$ sudo dmidecode -t 4 | egrep -i 'core (count|enabled)|thread count|Version'

The above discussed inbuilt Linux commands cover everything there is to know about the number of processors/cores in your Linux system and much more.

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How to find the number of CPU cores including virtual?

How do I find out the number of cores my CPU has, including virtual cores (hyper threading cores) using the command line?

6 Answers 6

cat /proc/cpuinfo | grep processor | wc -l 

To check the number of cores !

cat /proc/cpuinfo | grep 'core id' core id : 0 core id : 1 

Or lscpu will show you all output:

lscpu Architecture: i686 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 2 On-line CPU(s) list: 0,1 Thread(s) per core: 1 Core(s) per socket: 2 Socket(s): 1 Vendor ID: GenuineIntel CPU family: 15 Model: 4 Stepping: 7 CPU MHz: 2792.992 BogoMIPS: 5585.98 L1d cache: 16K L2 cache: 1024K 

nproc is also useful in scripts depending on the number of cores available to it. E.g. make -j$(nproc) .

To add to the existing answers, you can determine information about Intel’s HyperThreading by looking at the «siblings» line in /proc/cpuinfo. The example below is from a 2 socket machine. It shows the CPU has 6 cores but 12 «siblings». On Intel CPUs this means HyperThreading is enabled and there are 6 physical cores.

processor : 23 vendor_id : GenuineIntel cpu family : 6 model : 62 model name : Intel(R) Xeon(R) CPU E5-2430 v2 @ 2.50GHz stepping : 4 microcode : 0x428 cpu MHz : 1599.707 cache size : 15360 KB physical id : 1 siblings : 12 core id : 5 cpu cores : 6 apicid : 43 initial apicid : 43 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes 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 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm ida arat xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid fsgsbase smep erms bogomips : 5005.20 clflush size : 64 cache_alignment : 64 address sizes : 46 bits physical, 48 bits virtual power management: 

dmidecode is also useful for determining what hardware a Linux system is running on.

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