I have progressed a little further on this subject using multiple parallel tests for from 0 to ~25k biblios on a new, relatively fast server. In brief: 3.08 averages 0.88 secs per search 3.18 averages 5.06 secs for the same searches, but... 3.18 averages only 1.52 secs if I turn off facets. Facets appear to have a huge overhead in various components of Zebra, to the point where a single core of a multiple processor CPU gets overwhelmed, but does not share the load with other totally idle cores. Intel tell me that this is not fixable through any hardware/BIOS config and they are not aware of a Linux "standard library" that deals with processor affinity. I've searched around a little and found mentions for c and FORTRAN (marvelous old memories for me!) but so far nothing totally specific for Perl. taskset and sched_setaffinity might be usable at system level, and I might have a look at pthread_setaffinity_np.3.gz I've posted test results, notes and three sets of NYTProf analysis at <http://navalmarinearchive.com/z_koha/> and would appreciate if anyone has any suggestions or comparative tests and outcomes. Thanks and best regards -- Paul