> So the host will, if needs to reclaim those pages, carefully
> write their (useless) data out to swap first. This is a wasted
> effort which would be nice to avoid.
Now imagine after that some other short-lived application runs on the guest. The guest has no trouble to identify which pages to re-use (they're still no longer in use). But as soon as the guest touches the page, the host will first go and reclaim the original contents from its paging devices. And while writing out the page could be seen as just a "waste" from the guest's point of view, bringing the page back in actually delays the guest.
Needless to say that two stacked LRU mechanisms increase chances of this happening.
Copyright © 2018, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds