Hello, On Fri, Aug 11, 2023 at 05:01:08PM -0700, Yosry Ahmed wrote: > There have been a lot of problems coming from this global rstat lock: > hard lockups (when we used to flush atomically), unified flushing > being expensive, skipping flushing being inaccurate, etc. > > I wonder if it's time to rethink this lock and break it down into > granular locks. Perhaps a per-cgroup lock, and develop a locking > scheme where you always lock a parent then a child, then flush the > child and unlock it and move to the next child, etc. This will allow > concurrent flushing of non-root cgroups. Even when flushing the root, > if we flush all its children first without locking the root, then only > lock the root when flushing the top-level children, then some level of > concurrency can be achieved. > > Maybe this is too complicated, I never tried to implement it, but I > have been bouncing around this idea in my head for a while now. > > We can also split the update tree per controller. As far as I can tell > there is no reason to flush cpu stats for example when someone wants > to read memory stats. There's another thread. Let's continue there but I'm a bit skeptical whether splitting the lock is a good solution here. Regardless of locking, we don't want to run in an atomic context for that long anwyay. Thanks. -- tejun
