AMD athlon 64 Manuale Utente

40555

Rev. 3.00

June 2006

This following sections discuss tools and APIs available for assigning thread/process and memory 
affinity under various operating systems.

]. Additionally, libnuma, a shared library, is provided for more precise 

affinity control from within applications.

The Linux command-line utlities offer high-level affinity control options. The numactl utility is a 
command line tool for running a process with a specific node affinity.

For example, to run the 

foobar

 program on the cores of node 0, enter the following at the command 

prompt: 

numactl --cpubind=0  foobar

Application and kernel developers can use the libnuma shared library, which can be linked to 
programs and offers a stable API for setting thread affinity to a given node or set of nodes. Interested 
developers should consult the Linux man pages for details on the various functions available.

On a dual-core processor, a node has more than one core. If a process or thread is affined to a 
particular node using the tools or API discussed above, it may still migrate back and forth between the 
two cores of that node. This migration may or may not affect performance.

The taskset utility is a command-line tool for setting the process affinity for a specified program to 
any core. For example, to run program 

foobar

 on the two cores of node 0, enter the following on the 

command line: 

taskset -c 0,1  foobar

In SuSE Linux Enterprise Server 10/10.1, the numactl utility can be used instead of taskset to set 
process affinity to any core.

Linux provides several functions by which to set the thread affinity to any core or set of cores:

•

pthread_attr_setaffinity_np( ) and pthread_create( ) are provided as a part of the older nptl 
library; they can be used to set the affinity parameter and then create a thread using that affinity.

•

sched_setaffinity( ) system call and schedutils scheduler utilities.