On Wed, Mar 21, 2018 at 10:49:55AM +0300, Andrew Rybchenko wrote: > On 03/19/2018 08:11 PM, Olivier Matz wrote: > > > + * > > > + * if we don't need our mempools to have physically contiguous objects, > > > + * then just set page shift and page size to 0, because the user has > > > + * indicated that there's no need to care about anything. > > > + * > > > + * if we do need contiguous objects, there is also an option to reserve > > > + * the entire mempool memory as one contiguous block of memory, in > > > + * which case the page shift and alignment wouldn't matter as well. > > > + * > > > + * if we require contiguous objects, but not necessarily the entire > > > + * mempool reserved space to be contiguous, then there are two options. > > > + * > > > + * if our IO addresses are virtual, not actual physical (IOVA as VA > > > + * case), then no page shift needed - our memory allocation will give us > > > + * contiguous physical memory as far as the hardware is concerned, so > > > + * act as if we're getting contiguous memory. > > > + * > > > + * if our IO addresses are physical, we may get memory from bigger > > > + * pages, or we might get memory from smaller pages, and how much of it > > > + * we require depends on whether we want bigger or smaller pages. > > > + * However, requesting each and every memory size is too much work, so > > > + * what we'll do instead is walk through the page sizes available, pick > > > + * the smallest one and set up page shift to match that one. We will be > > > + * wasting some space this way, but it's much nicer than looping around > > > + * trying to reserve each and every page size. > > > + */ > > This comment is helpful to understand, thanks. > > > > (by the way, reading it makes me think we should rename > > MEMPOOL_F_*_PHYS_CONTIG as MEMPOOL_F_*_IOVA_CONTIG) > > I'll care about renaming in my patchset about mempool_ops API.
Great, thanks! Please also keep the old ones for now, we will remove them later.
