likwid-pin(1)
NAME
likwid-pin - pin a sequential or threaded application to dedicated processors
SYNOPSIS
likwid-pin [-vhSpqi] [-V verbosity] [-c corelist] [-s skip_mask]
DESCRIPTION
likwid-pin is a command line application to pin a sequential or multithreaded application to dedicated processors. It can be used as replacement for taskset. Opposite to taskset no affinity mask but single processors are specified. For multithreaded applications based on the pthread library the pthread_create library call is overloaded through LD_PRELOAD and each created thread is pinned to a dedicated processor as specified in core_list . Per default every generated thread is pinned to the core in the order of calls to pthread_create it is possible to skip single threads. The OpenMP implementations of GCC and ICC compilers are explicitly supported. Clang's OpenMP backend should also work as it is built on top of Intel's OpenMP runtime library. Others may also work likwid-pin sets the environment variable OMP_NUM_THREADS for you if not already present. It will set as many threads as present in the pin expression. Be aware that with pthreads the parent thread is always pinned. If you create for example 4 threads with pthread_create and do not use the parent process as worker you still have to provide num_threads+1 processor ids. likwid-pin supports different numberings for pinning. See section CPU EXPRESSION for details. For applications where first touch policy on NUMA systems cannot be employed likwid-pin can be used to turn on interleave memory placement. This can significantly speed up the performance of memory bound multithreaded codes. All NUMA nodes the user pinned threads to are used for interleaving.
OPTIONS
-h,--help
prints a help message to standard output, then exits.
-v,--version
prints version information to standard output, then exits.
-V, --verbose <level>
verbose output during execution for debugging. 0 for only
errors, 1 for informational output, 2 for detailed output and 3
for developer output
-c <cpu expression>
specify a numerical list of processors. The list may contain
multiple items, separated by comma, and ranges. For example
0,3,9-11. Other format are available, see the CPU EXPRESSION
section.
-s, --skip <mask>
Specify skip mask as HEX number. For each set bit the
corresponding thread is skipped.
-S,--sweep
All ccNUMA memory domains belonging to the specified thread list
will be cleaned before the run. Can solve file buffer cache
problems on Linux.
-p prints the available thread domains for logical pinning
-i set NUMA memory policy to interleave involving all NUMA nodes
involved in pinning
-q,--quiet
silent execution without output
CPU EXPRESSION
1. The most intuitive CPU selection method is a comma-separated list
of phyiscal CPU IDs. An example for this is 0,2 which schedules the
threads on CPU cores 0 and 2. The physical numbering also allows
the usage of ranges like 0-2 which results in the list 0,1,2.
2. The CPUs can be selected by their indices inside of an affinity
domain. The affinity domain is optional and if not given, Likwid
assumes the domain 'N' for the whole node. The format is
L:<indexlist> for selecting the CPUs inside of domain 'N' or
L:<domain>:<indexlist> for selecting the CPUs inside the given
domain. Assuming an virtual affinity domain 'P' that contains the
CPUs 0,4,1,5,2,6,3,7. After sorting it to have physical cores
first we get: 0,1,2,3,4,5,6,7. The logical numbering L:P:0-2
results in the selection 0,1,2 from the physical cores first list.
3. The expression syntax enables the selection according to an
selection function with variable input parameters. The format is
either E:<affinity domain>:<numberOfThreads> to use the first
<numberOfThreads> threads in affinity domain <affinity domain> or
E:<affinity domain>:<numberOfThreads>:<chunksize>:<stride> to use
<numberOfThreads> threads with <chunksize> threads selected in row
while skipping <stride> threads in affinity domain <affinity
domain>. Examples are E:N:4:1:2 for selecting the first four
physical CPUs on a system with 2 SMT threads per core or E:P:4:2:4
for choosing the first two threads in affinity domain P, skipping 2
threads and selecting again two threads. The resulting CPU list for
virtual affinity domain P is 0,4,2,6
3. The last format schedules the threads not only in a single affinity
domain but distributed them evenly over all available affinity
domains of the same kind. In contrast to the other formats, the
selection is done using the physical cores first and then the SMT
threads. The format is <affinity domain without number>:scatter
like M:scatter to schedule the threads evenly in all available
memory affinity domains. Assuming the two socket domains S0 =
0,4,1,5 and S1 = 2,6,3,7 the expression S:scatter results in the
CPU list 0,2,1,3,4,6,5,7
EXAMPLE
1. For standard pthread application:
likwid-pin -c 0,2,4-6 ./myApp
The parent process is pinned to processor 0 which is likely to be
thread 0 in ./myApp. Thread 1 is pinned to processor 2, thread 2 to
processor 4, thread 3 to processor 5 and thread 4 to processor 6. If
more threads are created than specified in the processor list, these
threads are pinned to processor 0 as fallback.
2. For selection of CPUs inside of a CPUset only the logical
numbering is allowed. Assuming CPUset 0,4,1,5:
likwid-pin -c L:1,3 ./myApp
This command pins ./myApp on CPU 4 and the thread started by ./myApp on
CPU 5
3. A common use-case for the numbering by expression is pinning of an
application on the Intel Xeon Phi coprocessor with its 60 cores
each having 4 SMT threads.
likwid-pin -c E:N:60:1:4 ./myApp
This command schedules one thread per physical CPU core for ./myApp.
AUTHOR
Written by Thomas Roehl <thomas.roehl@googlemail.com>.
BUGS
Report Bugs on <https://github.com/RRZE-HPC/likwid/issues>.
SEE ALSO
taskset(1), likwid-perfctr(1), likwid-features(1), likwid-topology(1),
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
