On Fri, Dec 14, 2018 at 12:17:08PM -0800, Dan Williams wrote: > On Fri, Dec 14, 2018 at 12:03 PM Matthew Wilcox <wi...@infradead.org> wrote: > > Yes; working on the pfn-to-page structure right now as it happens ... > > in the meantime, an XArray for it probably wouldn't be _too_ bad. > > It might... see the recent patch from Ketih responding to complaints > about get_dev_pagemap() lookup overhead:
Yeah, I saw. I called xa_dump() on the pgmap_array() running under QEmu and it's truly awful because the NVDIMMs presented by QEmu are very misaligned. If we can make the NVDIMMs better aligned, we won't hit such a bad case in the XArray data structure.
