On Tue, Oct 04, 2022 at 02:41:48AM +0000, Joel Fernandes (Google) wrote: > Implement timer-based RCU callback batching (also known as lazy > callbacks). With this we save about 5-10% of power consumed due > to RCU requests that happen when system is lightly loaded or idle. > > By default, all async callbacks (queued via call_rcu) are marked > lazy. An alternate API call_rcu_flush() is provided for the few users, > for example synchronize_rcu(), that need the old behavior. > > The batch is flushed whenever a certain amount of time has passed, or > the batch on a particular CPU grows too big. Also memory pressure will > flush it in a future patch. > > To handle several corner cases automagically (such as rcu_barrier() and > hotplug), we re-use bypass lists which were originally introduced to > address lock contention, to handle lazy CBs as well. The bypass list > length has the lazy CB length included in it. A separate lazy CB length > counter is also introduced to keep track of the number of lazy CBs. > > Suggested-by: Paul McKenney <paulmck@xxxxxxxxxx> > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> > --- > include/linux/rcupdate.h | 7 ++ > kernel/rcu/Kconfig | 8 ++ > kernel/rcu/rcu.h | 8 ++ > kernel/rcu/tiny.c | 2 +- > kernel/rcu/tree.c | 129 +++++++++++++++++++----------- > kernel/rcu/tree.h | 12 ++- > kernel/rcu/tree_exp.h | 2 +- > kernel/rcu/tree_nocb.h | 164 +++++++++++++++++++++++++++++++-------- > 8 files changed, 246 insertions(+), 86 deletions(-) > Tested-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> for whole v7 series. -- Uladzislau Rezki
