Following a recent discussion about hwloc being slow on large machines, I tried to write some doc talking about it and about XML import/export. Didn't know where to put it, so I added a FAQ section at the end of the doxy pages. Patch attached.
Brice
Index: doc/hwloc.doxy =================================================================== --- doc/hwloc.doxy (révision 2921) +++ doc/hwloc.doxy (copie de travail) @@ -1261,4 +1261,29 @@ hwloc_topology_get_online_cpuset() and other similar functions to filter the object that are relevant or not. + + +\page faq Frequently Asked Questions + +\section faq_xml I do not want hwloc to rediscover my enormous machine topology everytime I rerun a process + +Although the topology discovery is not expensive on common machines, +its overhead may become significant when multiple processes repeat +the discovery on large machines (for instance when starting one process +per core in a parallel application). +The machine topology usually does not vary much, except if some cores +are stopped/restarted or if the administrator restrictions are modified. +Thus rediscovering the whole topology again and again may look useless. + +For this purpose, hwloc offers XML import/export features. It lets you +save the discovered topology to a file (for instance with the lstopo program) +and reload it later by setting the HWLOC_XMLFILE environment variable. +Loading a XML topology is usually much faster than querying multiple +files or calling multiple functions of the operating system. +It is also possible to manipulate such XML files with the C programming +interface, and the import/export may also be directed to memory buffer +(that may for instance be transmitted between applications through a socket). + + + */
