David Laight <david.lai...@aculab.com> wrote: > > Add kunit tests to benchmark 256MiB copies to a UBUF iterator and an IOVEC > > iterator. This attaches a userspace VM with a mapped file in it > > temporarily to the test thread. > > Isn't that going to be completely dominated by the cache fills > from memory?
Yes... but it should be consistent in the amount of time that consumes since no device drivers are involved. I can try adding the same folio to the anon_file multiple times - it might work especially if I don't put the pages on the LRU (if that's even possible) - but I wanted separate pages for the extraction test. > I'd have thought you'd need to use something with a lot of > small fragments so that the iteration code dominates the copy. That would actually be a separate benchmark case which I should try also. > Some measurements can be made using readv() and writev() > on /dev/zero and /dev/null. Forget /dev/null; that doesn't actually engage any iteration code. The same for writing to /dev/zero. Reading from /dev/zero does its own iteration thing rather than using iterate_and_advance(), presumably because it checks for signals and resched. David
