On 15/11/22 10:32, Yury Norov wrote: > On Tue, Nov 15, 2022 at 05:24:56PM +0000, Valentin Schneider wrote: >> >> Is this meant as a replacement for [1]? > > No. Your series adds an iterator, and in my experience the code that > uses iterators of that sort is almost always better and easier to > understand than cpumask_nth() or cpumask_next()-like users. > > My series has the only advantage that it allows keep existing codebase > untouched. > Right >> I like that this is changing an existing interface so that all current >> users directly benefit from the change. Now, about half of the users of >> cpumask_local_spread() use it in a loop with incremental @i parameter, >> which makes the repeated bsearch a bit of a shame, but then I'm tempted to >> say the first point makes it worth it. >> >> [1]: https://lore.kernel.org/all/20221028164959.1367250-1-vschneid@xxxxxxxxxx/ > > In terms of very common case of sequential invocation of local_spread() > for cpus from 0 to nr_cpu_ids, the complexity of my approach is n * log n, > and your approach is amortized O(n), which is better. Not a big deal _now_, > as you mentioned in the other email. But we never know how things will > evolve, right? > > So, I would take both and maybe in comment to cpumask_local_spread() > mention that there's a better alternative for those who call the > function for all CPUs incrementally. > Ack, sounds good. > Thanks, > Yury
