"Adam 'WeirdArms' Wiggins" awiggins@cse.unsw.edu.au writes:
Can anyone explain whats different/new about the planned next-generation mapping tree for fiasco? I'd appreciate a detailed explination if anyones got the time.
The new thing about the new mapping database is that its data structures are much smaller. It uses compact linear arrays of fixed sizes, instead of elements linked in binary trees, to store the mapping trees for a given physical page frame.
The size of the current mapping database implementations (in L4/x86 and Fiasco) can become a severe problem: To support a heavily-loaded L4Linux, one eighth of the main memory has to reserved for mappings. This also has performance implications, as our AIM multiuser benchmark measurements show: If we steal original (monolithic) Linux one eighth of its main memory, the application-level performance penalty between Linux and L4Linux decreases from 3.8 percent to 2 percent (on our hardware).
Michael