Number of processors/cores in command line
Nice — but not as ubiquitous as /proc/cpuinfo. nproc is there on my ubuntu VM, but not on my RedHat 5.5-based machine.
Make sure to nproc —all for all installed Processing Units. Without —all , nproc only shows Processing Units available to the current process. Read the man page for more details. MMV.
You should link to: gnu.org/software/coreutils/manual/html_node/… The cyberciti page does not any more information than what is already mentioned here except showing more ads.
The most simplest tool comes with glibc and is called getconf :
$ getconf _NPROCESSORS_ONLN 4 Unfortunately, while this utility is available on Solaris, _NPROCESSORS_ONLN (or anything with cpu, proc, etc) is listed in its output. I was hoping since it’s a posix tool it’d work on Linux/Solaris so I didn’t have to use branching.
I think the method you give is the most portable on Linux. Instead of spawning unnecessary cat and wc processes, you can shorten it a bit:
$ grep --count ^processor /proc/cpuinfo 2 If you want to do this so it works on linux and OS X, you can do:
CORES=$(grep -c ^processor /proc/cpuinfo 2>/dev/null || sysctl -n hw.ncpu) On newer kernels you could also possibly use the the /sys/devices/system/cpu/ interface to get a bit more information:
$ ls /sys/devices/system/cpu/ cpu0 cpufreq kernel_max offline possible present release cpu1 cpuidle modalias online power probe uevent $ cat /sys/devices/system/cpu/kernel_max 255 $ cat /sys/devices/system/cpu/offline 2-63 $ cat /sys/devices/system/cpu/possible 0-63 $ cat /sys/devices/system/cpu/present 0-1 $ cat /sys/devices/system/cpu/online 0-1 See the official docs for more information on what all these mean.
nproc uses this, mostly ($OMP_NUM_THREADS then readdir sysfs). I think this one is the better interface.
When someone asks for «the number of processors/cores» there are 2 answers being requested. The number of «processors» would be the physical number installed in sockets on the machine.
The number of «cores» would be physical cores. Hyperthreaded (virtual) cores would not be included (at least to my mind). As someone who writes a lot of programs with thread pools, you really need to know the count of physical cores vs cores/hyperthreads. That said, you can modify the following script to get the answers that you need.
#!/bin/bash MODEL=`cat /cpu/procinfo | grep "model name" | sort | uniq` ALL=`cat /proc/cpuinfo | grep "bogo" | wc -l` PHYSICAL=`cat /proc/cpuinfo | grep "physical id" | sort | uniq | wc -l` CORES=`cat /proc/cpuinfo | grep "cpu cores" | sort | uniq | cut -d':' -f2` PHY_CORES=$(($PHYSICAL * $CORES)) echo "Type $MODEL" echo "Processors $PHYSICAL" echo "Physical cores $PHY_CORES" echo "Including hyperthreading cores $ALL" The result on a machine with 2 model Xeon X5650 physical processors each with 6 physical cores that also support hyperthreading:
Type model name : Intel(R) Xeon(R) CPU X5650 @ 2.67GHz Processors 2 Physical cores 12 Including hyperthreading cores 24 On a machine with 2 mdeol Xeon E5472 processors each with 4 physical cores that doesn’t support hyperthreading
Type model name : Intel(R) Xeon(R) CPU E5472 @ 3.00GHz Processors 2 Physical cores 8 Including hyperthreading cores 8 How to find the number of CPU cores including virtual?
How do I find out the number of cores my CPU has, including virtual cores (hyper threading cores) using the command line?
6 Answers 6
cat /proc/cpuinfo | grep processor | wc -l To check the number of cores !
cat /proc/cpuinfo | grep 'core id' core id : 0 core id : 1 Or lscpu will show you all output:
lscpu Architecture: i686 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 2 On-line CPU(s) list: 0,1 Thread(s) per core: 1 Core(s) per socket: 2 Socket(s): 1 Vendor ID: GenuineIntel CPU family: 15 Model: 4 Stepping: 7 CPU MHz: 2792.992 BogoMIPS: 5585.98 L1d cache: 16K L2 cache: 1024K nproc is also useful in scripts depending on the number of cores available to it. E.g. make -j$(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.
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?
Your image of text isn’t very helpful. It can’t be copied into an editor, and it doesn’t index very well, meaning that other users with the same problem are less likely to find the answer here. Please edit your post to incorporate the relevant text directly (preferably using copy+paste to avoid transcription errors).
@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