[PATCH 0/9] rcu: Support for lazy callbacks on !CONFIG_RCU_NOCB_CPU

From: Frederic Weisbecker
Date: Wed May 31 2023 - 06:17:59 EST


Here is a first attempt at providing support for lazy callbacks on
non-offloaded CPUs. I have measured interesting results on my machine
when it is mostly idle (just an idle ssh connection kept alive) with
a gain of +10% idle time. This needs more serious testing though,
especially to make sure that no performance regression is introduced.

Also I have only mildly tested on NOCB (eg: no rcutorture yet), so I
might have broken something.

Finally it's also possible that the idle time improvement is due to me
introducing a bug :)

The patches 1-5 can be considered independently from the rest.

Frederic Weisbecker (9):
rcu: Assume IRQS disabled from rcu_report_dead()
rcu: Use rcu_segcblist_segempty() instead of open coding it
rcu: Rename jiffies_till_flush to jiffies_lazy_flush
rcu: Introduce lazy queue's own qhimark
rcu: Add rcutree.lazy_enabled boot parameter
rcu/nocb: Rename was_alldone to was_pending
rcu: Implement lazyness on the main segcblist level
rcu: Make segcblist flags test strict
rcu: Support lazy callbacks with CONFIG_RCU_NOCB=n

.../admin-guide/kernel-parameters.txt | 5 +
include/linux/rcu_segcblist.h | 13 +-
kernel/rcu/Kconfig | 2 +-
kernel/rcu/rcu.h | 8 +-
kernel/rcu/rcu_segcblist.c | 44 ++-
kernel/rcu/rcu_segcblist.h | 32 +-
kernel/rcu/rcuscale.c | 6 +-
kernel/rcu/tree.c | 272 +++++++++++++++--
kernel/rcu/tree.h | 9 +-
kernel/rcu/tree_nocb.h | 285 +++++-------------
10 files changed, 425 insertions(+), 251 deletions(-)