The error I get from zynaddsubfx is: Cannot lock down 86611866 byte memory area (Cannot allocate memory) Cannot lock down 86611866 byte memory area (Cannot allocate memory) Segmentation fault (core dumped) davepl@ArbutnothL:~/pulseview> Unknown error... terminate called after throwing an instance of 'Jack::JackTemporaryException' what(): Works fine when jack is built without LTO.