On Sat, Oct 13, 2018 at 12:34:12AM -0700, John Hubbard wrote: > In patch 6/6, pin_page_for_dma(), which is called at the end of get_user_pages(), > unceremoniously rips the pages out of the LRU, as a prerequisite to using > either of the page->dma_pinned_* fields. > > The idea is that LRU is not especially useful for this situation anyway, > so we'll just make it one or the other: either a page is dma-pinned, and > just hanging out doing RDMA most likely (and LRU is less meaningful during that > time), or it's possibly on an LRU list. Have you done any benchmarking what this does to direct I/O performance, especially for small I/O directly to a (fast) block device?
