How to enable 256+ cores in Yakkety Server

By hifly

Yakkety Server uses generic kernel flavor. It is 4.8.0 Linux kernel.

While running on Intel KNL processor I cannot see cores above 256.

user@ubuntu02:~$ grep processor /proc/cpuinfo | wc -l
256

dmidecode shows real number of cores

user@ubuntu02:~$ sudo dmidecode -t 4
[sudo] password for user:
# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 3.0 present.

Handle 0x001B, DMI type 4, 48 bytes
Processor Information
    Socket Designation: CPU0
    Type: Central Processor
    Family: Xeon
    Manufacturer: Intel(R) Corporation
    ID: 71 06 05 00 FF FB EB BF
    Signature: Type 0, Family 6, Model 87, Stepping 1
    Flags:
            FPU (Floating-point unit on-chip)
            VME (Virtual mode extension)
            DE (Debugging extension)
            PSE (Page size extension)
            TSC (Time stamp counter)
            MSR (Model specific registers)
            PAE (Physical address extension)
            MCE (Machine check exception)
            CX8 (CMPXCHG8 instruction supported)
            APIC (On-chip APIC hardware supported)
            SEP (Fast system call)
            MTRR (Memory type range registers)
            PGE (Page global enable)
            MCA (Machine check architecture)
            CMOV (Conditional move instruction supported)
            PAT (Page attribute table)
            PSE-36 (36-bit page size extension)
            CLFSH (CLFLUSH instruction supported)
            DS (Debug store)
            ACPI (ACPI supported)
            MMX (MMX technology supported)
            FXSR (FXSAVE and FXSTOR instructions supported)
            SSE (Streaming SIMD extensions)
            SSE2 (Streaming SIMD extensions 2)
            SS (Self-snoop)
            HTT (Multi-threading)
            TM (Thermal monitor supported)
            PBE (Pending break enabled)
    Version: Intel(R) Xeon Phi(TM) Processor 000A @ 1.40GHz
    Voltage: 0.9 V
    External Clock: 100 MHz
    Max Speed: 4000 MHz
    Current Speed: 1400 MHz
    Status: Populated, Enabled
    Upgrade: <OUT OF SPEC>
    L1 Cache Handle: 0x0019
    L2 Cache Handle: 0x001A
    L3 Cache Handle: Not Provided
    Serial Number: To Be Filled By O.E.M.
    Asset Tag: To Be Filled By O.E.M.
    Part Number: To Be Filled By O.E.M.
    Core Count: 68
    Core Enabled: 68
    Thread Count: 272
    Characteristics:
            64-bit capable
            Multi-Core
            Hardware Thread
            Execute Protection
            Power/Performance Control

Is it possible to enable all 272 cores without recompiling kernel?

user@ubuntu02:~$ grep CONFIG_NR_CPUS /boot/config-4.8.0-32-generic
CONFIG_NR_CPUS=256

I think Ubuntu Server kernel flavor should be ready for it.

Source:: http://askubuntu.com/questions/870579/how-to-enable-256-cores-in-yakkety-server


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