Re: [RFC PATCH 0/4] Optimize rss_stat initialization/teardown for single-threaded tasks

[Mathieu Desnoyers]

On 2025-11-28 15:10, Jan Kara wrote:
> On Fri 28-11-25 08:30:08, Mathieu Desnoyers wrote:
[...]
> > I suspect that by doing just that we'd get most of the
> > performance benefits provided by the single-threaded special-case
> > proposed here.
>
> I don't think so. Because in the profiles I have been doing for these
> loads the biggest cost wasn't actually the per-cpu allocation itself but
> the cost of zeroing the allocated counter for many CPUs (and then the
> counter summarization on exit) and you're not going to get rid of that with
> just reshuffling per-cpu fields and adding slab allocator in front.

That's a good point ! So skipping the zeroing of per-cpu fields would
indeed justify special-casing the single-threaded case.

Thanks,

Mathieu

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com