Post Syndicated from original https://lwn.net/Articles/920891/

Memory allocation within the kernel is a complex business. The amount of
physical memory available on any given system will be strictly limited,
meaning that an allocation request can often only be satisfied by taking
memory from somebody else, but some of the options for reclaiming memory
may not be available when a request is made. Additionally,
some allocation requests have
requirements dictating where that memory can be placed or how quickly the
allocation must be made. The kernel’s
memory-allocation functions have long supported a set of “GFP flags” used
to describe the requirements of each specific request. Those flags will
probably undergo some changes soon as the result of this
patch set posted by Mel Gorman; that provides an opportunity to look at
those flags in some detail.