ASM:Topology

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Revision as of 11:19, 12 March 2014

ACPI Extended Topology

Building the Program

Prerequesites

• The Linux Operating System.
• Any Linux package which provides the taskset command that allows the Processor affinity.
  
  • ( util-linux if running ArchLinux. )
• The GNU gcc C compiler.

Getting the Source Files

In the repository, download the following files in a project directory, such as x2topology

• x2topology.c
• x2topology.sh
• Optionally, the binary executable file : x2topology

Compile the Source File

• Compile the C source file

gcc x2topology.c -o x2topology

• Give the executable permission to the downloaded Bash script

chmod +x x2topology.sh

Running x2topology

• Remark: You may add your project directory to the executable PATH, or invoke x2topology with a ./ prefix (meaning in the current directory)
  

Launch the x2topology.sh script which iterates through all the enabled Cores

./x2topology.sh

• Using a Core i7, Nehalem architecture, Hyper-threading and 4 Cores enabled, it outputs:

OS      APIC    Thread  Core
0x1     0       0       0
0x2     2       0       1
0x4     4       0       2
0x8     6       0       3
0x10    1       1       0
0x20    3       1       1
0x40    5       1       2
0x80    7       1       3

• Using a Core i7, Nehalem architecture, Hyper-threading disabled and 4 Cores enabled, it outputs:

OS      APIC    Thread  Core
0x1     0       0       0
0x2     2       0       1
0x4     4       0       2
0x8     6       0       3
0x10
0x20
0x40
0x80

• Using a Core i7, Nehalem architecture, Hyper-threading disabled and only 1 Core enabled (3 Cores disabled), it outputs:

OS      APIC    Thread  Core
0x1     0       0       0
0x2
0x4
0x8
0x10
0x20
0x40
0x80

where in the header text the following fields mean:

1. OS is the CPU mask as defined by the Linux Kernel, see man taskset
2. ACPI is the identifier of the physical or logical Core in a SMT architecture
3. Thread is the index number of a Thread inside a Core
4. Core is the index number of a Core inside a Processor package

Option

x2topology, binary or shell script can be launched with a verbose option to get details:

./x2topology -v
./x2topology.sh -v

Additional documentation

1. Intel® 64 Architecture Processor Topology Enumeration whitepaper
2. Intel 64 and IA-32 Software Developer Manual
3. Intel Processor Identification CPUID Instruction