When an important mmap event is missed perfparser can run into a cache-trashing loop

We might report the wrong mmap for some address to dwfl because perf may have dropped some mmap or reordered events across buffer flushes. The reported mmap may then overlap with some other mmap, which will cause dwfl to reject it. perfparser then clears the respective symbol table and the dwfl state and restarts reporting from a clean slate. This, however, can lead to the same error over and over, and perfparser might throw out the symbol table for every single sample. The analysis of the samples takes a very long time then.