Patching until the COWs come home (part 1)

Posted Mar 25, 2021 4:17 UTC (Thu) by alison (subscriber, #63752)
Parent article: Patching until the COWs come home (part 1)

Here is a naive question: why do we have both COW and RCU? Is there any reason fork() couldn't use RCU? Is RCU safer? RCU has extensive formal documentation but COW less so.

Patching until the COWs come home (part 1)

Posted Mar 25, 2021 7:29 UTC (Thu) by cladisch (✭ supporter ✭, #50193) [Link]

RCU requires that all software that accesses these data structures uses certain patterns and helper functions. (This is why we have many articles about it.)

COW uses the CPU's built-in virtual memory features to make it look to userspace software as if the pages were never shared to begin with.