On 6/26/26 16:38, Brendan Jackman wrote: > On Tue Apr 21, 2026 at 2:43 PM UTC, Lorenzo Stoakes wrote: >> On Fri, Apr 10, 2026 at 03:17:58PM +0000, Kalyazin, Nikita wrote: >>> From: Nikita Kalyazin <[email protected]> >>> >>> Let's convert set_direct_map_*() to take an address instead of a page to >>> prepare for adding helpers that operate on folios; it will be more >>> efficient to convert from a folio directly to an address without going >>> through a page first. > > Why is this more efficient? Isn't it a purely compile-time conversion? > > Indeed in the current implementation folio_address() is > page_address(&folio->page) so it still goes through a page anyway, no? > > I might be missing context here about how this will look in the > memdesc future.
Good question. page_address() is really only complicated for highmem. For non-highmem stuff it's simply derived from the page pfn. I suspect going page -> pfn will remain as efficient as it currently is (with vmemmap). For odd cases (SPARSEMEM without VMEMMAP) going through folio->pfn [1] might be slighty faster. [1] https://kernelnewbies.org/MatthewWilcox/Memdescs/Path -- Cheers, David
