On Wed, 13 Sept 2023 at 19:09, Andrey Konovalov <andreyknvl@xxxxxxxxx> wrote: > > 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. I may have gotten lost in the post-vacation email avalanche and missed it: did you already send the percpu-rwsem optimization? I am a little worried about the contention the plain rwlock introduces on big machines. Thanks, -- Marco
