  In the realm of shared memory systems, the challenge of reader-writer
synchronization is closely coupled with the potential for readers to access
outdated updates. Read-Copy-Update (RCU) is a synchronization primitive that
allows for concurrent and non-blocking read access to fresh data. This is
achieved through the creation of updated data copies, with each prior version
retained until all associated read-locks are released. Given the principle that
frequent updating keeps information fresh, the concern is whether we accumulate
an infinite number of update copies, leading to excessively large memory usage.
This paper analyzes trade-offs between memory usage and update age within
real-time status updating systems, focusing specifically on RCU. The analysis
demonstrates that with finite read time and read request rate, the average
number of updates within the system remains bounded.
