[PATCH v7 00/11] rcu: call_rcu() power improvements

[Joel Fernandes (Google)]

v7 version of RCU lazy patches based on rcu/next branch.

To facilitate easier merge, I dropped tracing and other patches and just
implemented the new changes. I will post the tracing patches later along with
rcutop as I need to add new tracepoints that Frederic suggested.

Main recent changes:
1. rcu_barrier() wake up only for lazy bypass list.
2. Make all call_rcu() default-lazy and add call_rcu_flush() API.
3. Take care of some callers using call_rcu_flush() API.
4. Several refactorings suggested by Paul/Frederic.
5. New call_rcu() to call_rcu_flush() conversions by Joel/Vlad/Paul.

I am seeing good performance and power with these patches on real ChromeOS x86
asymmetric hardware.

Earlier cover letter with lots of details is here:
https://lore.kernel.org/all/20220901221720.1105021-1-joel@xxxxxxxxxxxxxxxxx/

List of recent changes:
    
    [ Frederic Weisbec: Program the lazy timer only if WAKE_NOT, since other
      deferral levels wake much earlier so for those it is not needed. ]
    
    [ Frederic Weisbec: Use flush flags to keep bypass API code clean. ]
    
    [ Frederic Weisbec: Make rcu_barrier() wake up only if main list empty. ]
    
    [ Frederic Weisbec: Remove extra 'else if' branch in rcu_nocb_try_bypass(). ]
    
    [ Joel: Fix issue where I was not resetting lazy_len after moving it to rdp ]
    
    [ Paul/Thomas/Joel: Make call_rcu() default lazy so users don't mess up. ]
    
    [ Paul/Frederic : Cosmetic changes, split out wakeup of nocb thread. ]
    
    [ Vlad/Joel : More call_rcu -> flush conversions ]

Frederic Weisbecker (1):
rcu: Wake up nocb gp thread on rcu_barrier_entrain()

Joel Fernandes (Google) (7):
rcu: Make call_rcu() lazy to save power
rcu: Refactor code a bit in rcu_nocb_do_flush_bypass()
rcuscale: Add laziness and kfree tests
percpu-refcount: Use call_rcu_flush() for atomic switch
rcu/sync: Use call_rcu_flush() instead of call_rcu
rcu/rcuscale: Use call_rcu_flush() for async reader test
rcu/rcutorture: Use call_rcu_flush() where needed

Uladzislau Rezki (2):
scsi/scsi_error: Use call_rcu_flush() instead of call_rcu()
workqueue: Make queue_rcu_work() use call_rcu_flush()

Vineeth Pillai (1):
rcu: shrinker for lazy rcu

drivers/scsi/scsi_error.c |   2 +-
include/linux/rcupdate.h  |   7 ++
kernel/rcu/Kconfig        |   8 ++
kernel/rcu/rcu.h          |   8 ++
kernel/rcu/rcuscale.c     |  67 +++++++++++-
kernel/rcu/rcutorture.c   |  16 +--
kernel/rcu/sync.c         |   2 +-
kernel/rcu/tiny.c         |   2 +-
kernel/rcu/tree.c         | 140 +++++++++++++++++--------
kernel/rcu/tree.h         |  12 ++-
kernel/rcu/tree_exp.h     |   2 +-
kernel/rcu/tree_nocb.h    | 213 ++++++++++++++++++++++++++++++++------
kernel/workqueue.c        |   2 +-
lib/percpu-refcount.c     |   3 +-
14 files changed, 388 insertions(+), 96 deletions(-)

--
2.38.0.rc1.362.ged0d419d3c-goog