I am reading posts about memory barriers.

About LoadLoad barrier, the blog said:

there’s no guarantee that #LoadLoad will pull the latest, or head, revision of the entire repository! It could very well pull an older revision than the head, as long as that revision is at least as new as the newest value which leaked from the central repository into his local machine

I think it indicates that all value updated before the latest value shall be synchronized to the processor.

But how can the memory know the time when each value is updated?
Does not this log consume a lot of space?