On 11/17/2022 2:23 PM, Valentin Schneider wrote:

On 15/11/22 10:32, Yury Norov wrote:

quoted

On Tue, Nov 15, 2022 at 05:24:56PM +0000, Valentin Schneider wrote:

quoted

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

quoted

quoted

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@redhat.com/ (local)

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.

Good.
Is a respin needed, to add the comment mentioned above?