Re: [PATCH 11/15] stackdepot: use read/write lock

[Andrey Konovalov]

On Tue, Sep 5, 2023 at 6:19 PM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> > Good suggestion. I propose that we keep the rwlock for now, and I'll
> > check whether the performance is better with percpu-rwsem once I get
> > to implementing and testing the performance changes. I'll also check
> > whether percpu-rwsem makes sense for stack ring in tag-based KASAN
> > modes.
>
> I think it's quite obvious that the percpu-rwsem is better. A simple
> experiment is to measure the ratio of stackdepot hits vs misses. If
> the ratio is obviously skewed towards hits, then I'd just go with the
> percpu-rwsem.
>
> The performance benefit may not be measurable if you use a small system.

I started looking into using percpu-rwsem, but it appears that it
doesn't have the irqsave/irqrestore API flavor. I suspect that it
shouldn't be hard to add it, but I'd rather not pursue this as a part
of this series.

So I still propose to keep the rwlock for now, and switch to
percpu-rwsem later together with the other perf changes.