LIBSYSCONFCPUS 0.5 ================== by Kevin Pulo, kev@pulo.com.au 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 <kev@pulo.com.au>. SEE ALSO -------- - ltrace - strace