On Tue, Feb 09, 2021 at 01:32:58PM -0800, Jesse Barnes wrote: > > ====================== > > Augmented Page Reclaim > > ====================== > > We would like to share a work with you and see if there is enough > > interest to warrant a run for the mainline. This work is a part of > > result from a decade of research and experimentation in memory > > overcommit at Google: an augmented page reclaim that, in our > > experience, is performant, versatile and, more importantly, simple. > > Per discussion on IRC, maybe some additional background would help. And I'll add more details to the doc included in the tree once I've finished collecting feedback. > In looking at browser workloads on Chrome OS, we found that reclaim was: > 1) too expensive in terms of CPU usage We have two general metrics for this item: CPU time spent on page reclaim and (direct) page reclaim latency. CPU usage is important to everybody but latency is also quite important for phones, laptops, etc. > 2) often making poor decisions about what to reclaim We have another two metrics here: the number of refaults and the number of false inactive pages. For example, it's bad if pages refault within a hundred of milliseconds after they have been reclaimed. Also it's bad if reclaim thinks many pages are inactive but later finds they are actually active. > This work was mainly targeted toward improving those things, with an > eye toward interactive performance for browser workloads. > > We have a few key tests we use for that, that measure tab switch times > and number of tab discards when under memory pressure, and this > approach significantly improves these (see Yu's data). We monitor workload-specific metrics as well. For example, we found page reclaim also affects battery life, tab switch latency and the number of janks (pauses when scrolling web pages) on Chrome OS. I don't want to dump everything here because they seem irrelevant to most people. > We do expect this approach will also be beneficial to cloud workloads, > and so are looking for people to try it out in their environments with > their favorite key tests or workloads. And if you are interested in our workload-specific metrics, Android, Cloud, etc., please feel free to contact us. Any other questions, concerns and suggestions are also welcome.
