Appendix C AFB Interface

In this appendix, we describe an initial version of the AFB interface. We specify it as a system-call oriented interface between the operating system and the application programs. We refer to pages in a virtual memory address space by symbolic names like a i and b, although the actual interface will require the use of each page's actual virtual memory address. SAPPs are assigned unique identifiers. The following are the system calls provided by the AFB interface for manipulating SAPPs: • PAF-define (a 1 , a 2 ,..., a n). This defines a SAPP consisting of the pages a 1 , a 2 ,..., a n. It returns a SAPP identifier. • PAF-add (B, b). This adds page b to SAPP B. • PAF-remove (B, b). This removes page b from SAPP B. • PAF-delete (B). This removes SAPP B from the page flush policy. The following are provided for establishing propagation precedence constraints between SAPPs: • PFB-add (A, B). This specifies and introduces a A ≤p B rule. A and B can be references to individual pages as well (this applies for all the PFB and flush-lock calls). • PFB-delete (A, B). This removes a A ≤p B rule from the flush policy. The number of PFB-add calls and PFB-delete calls for the particular pair A and B must match before the rule is removed. A stronger version of this delete call can be provided which does not have this requirement. The following are the system calls provided by the AFB interface for flush-locking and flushing SAPPs: • flush-lock (A). This flush-locks the SAPP A. Flush-locks are fully compatible with all other lock modes. • flush-unlock (A). This releases the flush-lock being held on SAPP A. Unlocks have to match locks before the lock on A is actually released. • flush-request (A). This call informs the operating system that it should favour the propagation of SAPP A. The page flush policy must still be adhered to. A blocking version of this call can also be provided. The blocking version is similar to an explicit write operation except that page flush rules are adhered to.