On Tue, Aug 18, 2020 at 04:43:14PM +0200, Thomas Gleixner wrote: > On Tue, Aug 18 2020 at 06:53, Paul E. McKenney wrote: > > On Tue, Aug 18, 2020 at 09:43:44AM +0200, Michal Hocko wrote: > >> Thomas had a good point that it doesn't really make much sense to > >> optimize for flooders because that just makes them more effective. > > > > The point is not to make the flooders go faster, but rather for the > > system to be robust in the face of flooders. Robust as in harder for > > a flooder to OOM the system. > > > > And reducing the number of post-grace-period cache misses makes it > > easier for the callback-invocation-time memory freeing to keep up with > > the flooder, thus avoiding (or at least delaying) the OOM. > > Throttling the flooder is incresing robustness far more than reducing > cache misses. True, but it takes time to identify a flooding event that needs to be throttled (as in milliseconds). This time cannot be made up. And in the absence of a flooding event, the last thing you want to do is to throttle call_rcu(), kfree_rcu(), and kvfree_rcu(). Thanx, Paul
