On Sun, Oct 25, 2020 at 09:44:07PM -0700, John Hubbard wrote: > On 10/25/20 9:21 PM, Matthew Wilcox wrote: > > I don't think the page pinning approach is ever valid. For file > > Could you qualify that? Surely you don't mean that the entire pin_user_pages > story is a waste of time--I would have expected you to make more noise > earlier if you thought that, yes? I do think page pinning is the wrong approach for everything. I did say so at the time, and I continue to say so when the opportunity presents itself. But shouting about it constantly only annoys people, so I don't generally bother. I have other things to work on, and they're productive, so I don't need to spend my time arguing. > > It's been five years since DAX was merged, and page pinning still > > doesn't work. How much longer before the people who are pushing it > > realise that it's fundamentally flawed? > > Is this a separate rant about *only* DAX, or is general RDMA in your sights > too? :) This is a case where it's not RDMA's _fault_ that there's no good API for it to do what it needs to do. There's a lot of work needed to wean Linux device drivers off their assumption that there's a struct page for every byte of memory.
