What is the cost of RCU in terms of memory and complexity?
Writers pay more: they must copy the data, mutate it, and then wait for a grace period before reclamation. Memory use increases transiently (both versions coexist). Synchronization is complex—developers must understand quiescent states, grace periods, and RCU synchronize semantics to avoid use-after-free bugs.
Answered in
How Linux RCU Unlocks Read-Side ScalingRCU lets millions of readers run lock-free while a single writer updates state by copying, mutating off-to-the-side, and atomically flipping a pointer.
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