Stack Overflow have a habit of migrating questions to other sites that they shouldn't. It's an inherent problem with having a site that permits any group of 5 users with migration rights to move a question (but a necessary problem; without it all the sites would just be a mess of questions that don't belong).
Steps are being taken to try and avoid these poor migrations. But one thing we generally don't do it migrate a question back to where it came from, because they have already indicated that they don't believe it fits their scope (as sysadmin1138 notes, the question is un-migrated from the source site, but stays closed so that it can be re-opened).
Your question fits a real grey area that falls between a few different sites. It could be suitable for Stack Overflow (but not really as it's about benchmarking, not programming). It could be suitable for Server Fault (but not really, as it's not within the sort of scope we deal with as defined by the [FAQ]). It could be suitable for Unix & Linux due to its POSIX nature, as it seems related to fairly low-level stuff, but I most of us are wary of migrating stuff there as we don't really know if it fits their scope or not.
Ultimately I'd actually suggest posting your question over on Unix & Linux and see how you go. On second thoughts, after re-reading the question, I'm not sure that's appropriate either...