Since the modified version of rcu-poll was unable to match the performance of rcu-ltimer, and since there are currently no known uses of RCU that require low grace-period latency, rcu-ltimer is used in the Linux 2.5 kernel. If needed, we will investigate use of rcu-poll's grace-period-latency mechanisms in rcu-ltimer after a fixed delay. A modified version of rcu-sched may attain even lower overheads than those of rcu-ltimer.
We will continue investigating how RCU may be used
in the Linux kernel, including using it to provide NMI handler support
and applying it to the tasklist_lock
to eliminate some starvation scenarios that have been observed
in the Linux 2.5 kernel.
Experience gained from use of RCU in DYNIX/ptx
, K42 [Gamsa99],
and Linux indicate that it will continue to be quite helpful in
obtaining dramatic performance improvements with little increase in
complexity.