On Thu, Dec 03, 2020 at 05:36:07PM -0500, Johannes Weiner wrote: > Correct, it's only interesting for pages under LRU management - page > cache and swap pages. It should not matter for direct IO. > > The VM uses the page flag to tell the difference between cold faults > (empty cache startup e.g.), and thrashing pages which are being read > back not long after they have been reclaimed. This influences reclaim > behavior, but can also indicate a general lack of memory. I really wonder if we should move setting the flag out of bio_add_page and into the writeback code, as it will do the wrong things for non-writeback I/O, that is direct I/O or its in-kernel equivalents.
