On Wed, Jun 24, 2020 at 08:14:17PM +0100, Chris Wilson wrote: > A general rule of thumb is that shrinkers should be fast and effective. > They are called from direct reclaim at the most incovenient of times when > the caller is waiting for a page. If we attempt to reclaim a page being > pinned for active dma [pin_user_pages()], we will incur far greater > latency than a normal anonymous page mapped multiple times. Worse the > page may be in use indefinitely by the HW and unable to be reclaimed > in a timely manner. A pinned page can't be migrated, discarded or swapped by definition - it would cause data corruption. So, how do things even get here and/or work today at all? I think the explanation is missing something important. Jason
