Making The Common Case The Only Case With Anticipatory Memory Allocation

We present anticipatory memory allocation (AMA), a new method to build kernel code that is robust to memory-allocation failures. AMA avoids the usual difficulties in handling allocation failures through a novel combination of static and dynamic techniques. Specifically, a developer, with assistance from AMA static analysis tools, determines how much memory a particular call into a kernel subsystem will need, and then preallocates said amount immediately upon entry to the kernel; subsequent allocation requests are serviced from the preallocated pool and thus guaranteed never to fail. We describe the static and runtime components of AMA, and then present a thorough evaluation of Linux ext2-mfr, a case study in which we transform the Linux ext2 file system into a memory-failure robust version of itself. Experiments reveal that ext2-mfr avoids memory-allocation failures successfully while incurring little space or time overhead.