How to detect E-cores and P-cores in Linux alder lake system?

Question

How can I check particular cpu core belongs to P-core or E-core group? Is there any way to list information about Performance/Energy cores in a running Linux x86_64 alder lake system? Like, Printing any of the sysfs parameters?

Answer 1

We can identify which core has SMT (hyper-threading) enabled. Run:

lscpu --all --extended

This is the result for 12900K:

➜ lscpu --all --extended
CPU NODE SOCKET CORE L1d:L1i:L2:L3 ONLINE    MAXMHZ   MINMHZ
  0    0      0    0 0:0:0:0          yes 6700.0000 800.0000
  1    0      0    0 0:0:0:0          yes 6700.0000 800.0000
  2    0      0    1 1:1:1:0          yes 6700.0000 800.0000
  3    0      0    1 1:1:1:0          yes 6700.0000 800.0000
  4    0      0    2 2:2:2:0          yes 6500.0000 800.0000
  5    0      0    2 2:2:2:0          yes 6500.0000 800.0000
  6    0      0    3 3:3:3:0          yes 6500.0000 800.0000
  7    0      0    3 3:3:3:0          yes 6500.0000 800.0000
  8    0      0    4 4:4:4:0          yes 6500.0000 800.0000
  9    0      0    4 4:4:4:0          yes 6500.0000 800.0000
 10    0      0    5 5:5:5:0          yes 6500.0000 800.0000
 11    0      0    5 5:5:5:0          yes 6500.0000 800.0000
 12    0      0    6 6:6:6:0          yes 6500.0000 800.0000
 13    0      0    6 6:6:6:0          yes 6500.0000 800.0000
 14    0      0    7 7:7:7:0          yes 6500.0000 800.0000
 15    0      0    7 7:7:7:0          yes 6500.0000 800.0000
 16    0      0    8 8:8:8:0          yes 3900.0000 800.0000
 17    0      0    9 9:9:8:0          yes 3900.0000 800.0000
 18    0      0   10 10:10:8:0        yes 3900.0000 800.0000
 19    0      0   11 11:11:8:0        yes 3900.0000 800.0000
 20    0      0   12 12:12:9:0        yes 3900.0000 800.0000
 21    0      0   13 13:13:9:0        yes 3900.0000 800.0000
 22    0      0   14 14:14:9:0        yes 3900.0000 800.0000
 23    0      0   15 15:15:9:0        yes 3900.0000 800.0000

Now, look at the CPU column and CORE column. For example:

• CPU 0 and CPU 1 belong to CORE 0. Therefore, CORE 0 is a P-core with SMT.
• CPU 16 belongs to CORE 8. Therefore, CORE 8 is an E-core.

Note that this method will only work if you haven't explicitly disabled P-core's SMT in BIOS. If you disabled SMT in BIOS, you may look at the MAXMHZ column as suggested in Peter's comment.

Answer 2

A more precise answer that doesn't require guessing based on processor characteristics like frequency or number of threads, is that this information is exposed in the /sys pseudo filesystem:

On Alder lake (and mostly like other hybrid Intel architectures), instead of /sys/devices/cpu there are two directories: /sys/devices/cpu_atom/ and /sys/devices/cpu_core/, being the first (cpu_atom) for the e-cores and the second (cpu_core) for the p-cores.

Inside each directory there is a file named cpus that contain the cpu range number.

For example, in my i7-1360P:

• /sys/devices/cpu_core/cpus contain 0-7 (four p-cores with two threads each)
• /sys/devices/cpu_atom/cpus contain 8-15