On Tue, Jun 03, 2025 at 04:18:22PM +0200, Christian König wrote: > > Does it matter compared to the I/O in this case? > > It unfortunately does, see the numbers on patch 3 and 4. That's kinda weird. Why does the page table lookup tage so much time compared to normal I/O? > My question is rather if it's ok to call f_op->write_iter() and > f_op->read_iter() with pages allocated by alloc_pages(), e.g. > where drivers potentially ignore the page count and just re-use pages > as they like? read_iter and write_iter with ITER_BVEC just use the pages as source and destination of the I/O. They must not touch the refcounts or do anything fancy with them. Various places in the kernel rely on that.
