Making decisions based on up to 2 s old information. On Tue, Mar 01, 2022 at 09:21:12AM -0800, Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > Without flushing the worst that can happen in the refault path is > false (or missed) activations of the refaulted page. Yeah, this may under- or overestimate workingset size (when it's changing), the result is likely only less efficient reclaim. > For reclaim code, some heuristics (like deactivating active LRU or > cache-trim) may act on old information. Here, I'd be more careful whether such a delay cannot introduce some unstable behavior (permanent oscillation in the worst case). > Now, coming to your question, yes, we can remove the flushing from > these performance critical codepaths as the stats at most will be 2 > second old due to periodic flush. Another aspect is that people will notice and report such a narrowly located performance regression more easily than reduced/less predictable reclaim behavior. (IMO the former is better, OTOH, it can also be interpreted that noone notices (is able to notice).) Michal
