Extend cpu_count() API to get sockets and NUMA nodes count

I could not find anything related in the documentation. I am currently using a “hack” working on some Intel-based systems: Messing around with temperature sensors, but it really is not clean …

len([
    None for sensor in psutil.sensors_temperatures()['coretemp']
    if 'Physical id' in sensor.label
    ])

EDIT: The above is working on Linux x86_64 for 4.4, 4.10 and 4.15 kernels.

[giampaolo]

OK, here’s a bit of brainstorming. Currently psutil is able to return logical (hyper threading) and physical cores. The goal is to provide CPU sockets count (and possibly others). IMO, the ideal API if we were to start from scratch today would be having a single function accepting a kind parameter, similar to psutil.net_connections(kind='all'). That would be simple and extensible in terms of back compatibility. It would look like this:

# number of logical / hyper-threading CPU cores, same as os.cpu_count()
psutil.cpu_count(kind="logical")  

# number of physical cores (currently supported on all platforms except OpenBSD and NetBSD)
psutil.cpu_count(kind="cores")

# number of sockets
psutil.cpu_count(kind="sockets")  

# number of usable CPUs, aka len(os.sched_getaffinity(0)) on Linux
# or len(psutil.Process().cpu_affinity())
psutil.cpu_count(kind="usable")

# number of NUMA nodes
psutil.cpu_count(kind="numa")

(similarly to os.cpu_count(), if the value can’t be determined we’ll just return None)

The current function signature unfortunately is:

psutil.cpu_count(logical=True)

What we MAY do in order to keep supporting logical parameter and avoid code breakage is this:

psutil.cpu_count(kind='logical', logical=None)

If the function is invoked as such we will assume the user is asking for logical cores:

>>> psutil.cpu_count()
8
>>> psutil.cpu_count(True)
DeprecationWarning('use of boolean as first parameter is deprecated, use kind="logical"')
8
>>> psutil.cpu_count(logical=True)
DeprecationWarning('"logical" parameter is deprecated, use kind="logical"')
8

If the function is invoked as such we will assume the user is asking for physical cores:

>>> psutil.cpu_count(False)
DeprecationWarning('use of boolean as first parameter is deprecated; use kind="cores"')
4
>>> psutil.cpu_count(logical=False)
DeprecationWarning('"logical" parameter is deprecated; use kind="cores"')
4

[santagada]

I think calling all that cpu just makes the code more confusing, why not: numa_count(), group_count(), socket_count(), cpu_count(group=<groupnumber>, numa=<numanumber>) ?

Then you can get the number of logical/physical cpus in a group or numa node and also the numa and group count. For windows you still need to know in which group is each numa node so something like numa_group(numa=<numanumber>) is also needed.

A numa node has a group (on cpus with more than 64 logical cores in the same numa node windows actually creates virtual numa nodes for them) and an affinity mask in that group as sometimes machines with < 64 total logical cpus but more than one numa node will get their cpus as different affinity masks on the same group

eg. a 2 socket machine with two 20 logical core die will get 2 numa nodes, 1 group and an affinity mask of the first 20 logical cores for numa node 1 and the rest for numa node 2.