Sorry for being so slow to get to this...it fell into a dark crack in my rickety email folder hierarchy. I do have one question... On Fri, 17 Aug 2018 17:47:16 +0300 Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> wrote: > + ``GFP_HIGHUSER_MOVABLE`` does not require that allocated memory > + will be directly accessible by the kernel or the hardware and > + implies that the data is movable. > + > + ``GFP_HIGHUSER`` means that the allocated memory is not movable, > + but it is not required to be directly accessible by the kernel or > + the hardware. An example may be a hardware allocation that maps > + data directly into userspace but has no addressing limitations. > + > + ``GFP_USER`` means that the allocated memory is not movable and it > + must be directly accessible by the kernel or the hardware. It is > + typically used by hardware for buffers that are mapped to > + userspace (e.g. graphics) that hardware still must DMA to. I realize that this is copied from elsewhere, but still...as I understand it, the "HIGH" part means that the allocation can be satisfied from high memory, nothing more. So...it's irrelevant on 64-bit machines to start with, right? And it has nothing to do with DMA, I would think. That would be handled by the DMA infrastructure and, perhaps, the DMA* zones. Right? I ask because high memory is an artifact of how things are laid out on 32-bit systems; hardware can often DMA quite easily into memory that the kernel sees as "high". So, to me, this description seems kind of confusing; I wouldn't mention hardware at all. But maybe I'm missing something? Thanks, jon
