Understanding output of lscpu
“CPU(s): 56” represents the number of logical cores, which equals “Thread(s) per core” × “Core(s) per socket” × “Socket(s)”. One socket is one physical CPU package (which occupies one socket on the motherboard); each socket hosts a number of physical cores, and each core can run one or more threads. In your case, you have two sockets, each containing a 14-core Xeon E5-2690 v4 CPU, and since that supports hyper-threading with two threads, each core can run two threads.
“NUMA node” represents the memory architecture; “NUMA” stands for “non-uniform memory architecture”. In your system, each socket is attached to certain DIMM slots, and each physical CPU package contains a memory controller which handles part of the total RAM. As a result, not all physical memory is equally accessible from all CPUs: one physical CPU can directly access the memory it controls, but has to go through the other physical CPU to access the rest of memory. In your system, logical cores 0–13 and 28–41 are in one NUMA node, the rest in the other. So yes, one NUMA node equals one socket, at least in typical multi-socket Xeon systems.
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cph_sto
Updated on September 18, 2022Comments
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cph_sto over 1 year
You can see the output from
lscpu
command -jack@042:~$ 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: 79 Model name: Intel(R) Xeon(R) CPU E5-2690 v4 @ 2.60GHz Stepping: 1 CPU MHz: 2600.000 CPU max MHz: 2600.0000 CPU min MHz: 1200.0000 BogoMIPS: 5201.37 Virtualization: VT-x Hypervisor vendor: vertical Virtualization type: full 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
I can see that there are
2
sockets (which is like a processor ??) and inside each of the socket we have14
cores. So, in total2x14=28
physical cores. Normally, a CPU can contain multiple cores, so number of CPUs can never be smaller than number of Cores. But, as shown in the outputCPUs(s): 56
and this is what is confusing me.I can see that
Thread(s) per core: 2
, so these28
cores can behave like2x28=56
logical cores.Question 1: What does this
CPUs(s): 56
denote? DoesCPU(s)
denote number of Virtual/Logical core, as it cannot be a Physical core core atleast?Question 2: What does this
NUMA node
mean? Does it represent the socket? -
cph_sto over 5 yearsStefan, in this en.wikipedia.org/wiki/Non-uniform_memory_access#/media/… (courtesy Wikipedia link you referred in your post) - Are there 2 NUMA nodes on each socket? As I understood, in this configuration, RAM is 32 GB and each Socket has 2 NUMA nodes, with each node being shared by 1 CPU Packages consisting of 8 processors, logical or otherwise. Am I correct? In my system, as you also mentioned, there is one NUMA node per socket (NUMA node0 CPU(s): 0-13,28-41). So, I suppose this pic is not an abstraction of the architecture of my system.??
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Stephen Kitt over 5 yearsThat image shows the NUMA architecture of a Bulldozer CPU; your Xeon CPU has a different architecture. NUMA layouts depend on the memory controllers, not the sockets (directly); you can have one memory controller per socket (as on current Xeon), multiple memory controllers per socket, or even external memory controller(s) instead.