--vec overhead because of poor hwloc usage

[philipportner]

Currently, when running DAPHNE with the --vec flag, the usage of hwloc_topology_load() inside of MTWrapperBase causes a significant overhead in execution time as this is repeated for every single call to a _vectorizedPipeline__* kernel. This causes us to repeatedly read sysfs files which each needs multiple syscalls.

Possible solutions could be:

• filter unnecessary information with hwloc_topology_set_all_types_filter
• generate them once with lstopo and use HWLOC_XMLFILE=/path/to/topology.xml and HWLOC_THISSYSTEM=1
• ideally, we get all hwloc queries out of the _vectorizedPipeline__* kernel to not repeat this work
• other solutions

[philipportner]

This is part of the problem that causes a script that runs in ~0.25s without --vec to explode up to ~6.2s with --vec