GitHub - stylight/libsysconfcpus: A github mirror of http://www.kev.pulo.com.au/libsysconfcpus/

Branches Tags

Name		Name	Last commit message	Last commit date
Latest commit History 4 Commits
src		src
AUTHORS		AUTHORS
COPYING		COPYING
ChangeLog		ChangeLog
INSTALL		INSTALL
Makefile.am		Makefile.am
Makefile.in		Makefile.in
NEWS		NEWS
README		README
aclocal.m4		aclocal.m4
compile		compile
config.guess		config.guess
config.h.in		config.h.in
config.sub		config.sub
configure		configure
configure.ac		configure.ac
depcomp		depcomp
install-sh		install-sh
ltmain.sh		ltmain.sh
missing		missing

Repository files navigation

LIBSYSCONFCPUS 0.5
==================

by Kevin Pulo, [email protected]
http://www.kev.pulo.com.au/libsysconfcpus/
Copyright (c) 2008-2009
Licensed under the GNU GPL v2 or higher, as per the COPYING file.


DESCRIPTION
-----------

libsysconfcpus is an $LD_PRELOAD library that intercepts calls to sysconf(),
and adjusts the responses for _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN,
which are used to determine the number of processors available (either
configured or online) at runtime in a system.  Unfortunately, some closed-
source software assumes that all of these processors may be used for
computation, which is an assumption that is frequently not true on multiuser
and HPC systems.  Thus, libsysconfcpus provides a simple, non-intrusive way of
adjusting the behaviour of such software (when it is dynamically linked).

In addition, libsysconfcpus is a small, simple example of how to use
$LD_PRELOAD to do function call interception on glibc and POSIX systems.  It is
hoped that it is useful not only inherently, but also for learning about
$LD_PRELOAD, and as a template or skeleton LD_PRELOAD library.  Its
from-scratch development was used to illustrate LD_PRELOAD usage in the "Fun
with LD_PRELOAD" presentation by the author at linux.conf.au 2009 in Hobart.


INSTALLATION
------------

Standard autoconf process:  ./configure && make && make install


USAGE
-----

    sysconfcpus [options] <program> [args...]

Valid options are:

    -v, --version   Display the sysconfcpus version
    -h, --help      Display this help
    -d, --debug     Display debug info

    -n, --num <n>   Number of processors (both conf and onln)
    -c, --conf <n>  Number of processors (conf(igured))
    -o, --onln <n>  Number of processors (online)


EXAMPLEs
--------

$ test-sysconfcpus 
sysconf(_SC_NPROCESSORS_CONF) = 2
sysconf(_SC_NPROCESSORS_ONLN) = 2
$ sysconfcpus -n 8 test-sysconfcpus 
sysconf(_SC_NPROCESSORS_CONF) = 8
sysconf(_SC_NPROCESSORS_ONLN) = 8
$ sysconfcpus -c 8 -o 6 test-sysconfcpus 
sysconf(_SC_NPROCESSORS_CONF) = 8
sysconf(_SC_NPROCESSORS_ONLN) = 6
$ 


LIMITATIONS
-----------

- Only dynamically linked binaries


FEEDBACK
--------

Comments, feature suggestions, bug reports, patches, etc are most
welcome, please send them to Kevin Pulo <[email protected]>.


SEE ALSO
--------

- ltrace
- strace