Re: [PATCH v9 00/13] rcu: call_rcu() power improvements

[Joel Fernandes]

On Mon, Oct 17, 2022 at 9:37 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> On Sun, Oct 16, 2022 at 04:22:52PM +0000, Joel Fernandes (Google) wrote:
> > v9 version of RCU lazy patches based on rcu/next branch.
> >  Only change since v8 is this discussion:
> >  https://lore.kernel.org/rcu/20221011180142.2742289-1-joel@xxxxxxxxxxxxxxxxx/T/#m8eff15110477f3430b3b02561b66f7b0d34a73b0
> >
> > 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/
> >
[...]
>
> Very good, thank you all!
>
> I have pulled these in for further review and testing.
>
> I am holding off on the last one ("rcu/debug: Add wake-up debugging for
> lazy callbacks") for the immediate future, but let's see how it goes.

Thanks! And nice timing with RCU just turning 20 years old ;-)

 - Joel




>
>                                                         Thanx, Paul
>
> > Frederic Weisbecker (1):
> > rcu: Fix missing nocb gp wake on rcu_barrier()
> >
> > Joel Fernandes (Google) (9):
> > 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
> > rxrpc: Use call_rcu_flush() instead of call_rcu()
> > rcu/debug: Add wake-up debugging for lazy callbacks
> >
> > 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        |  15 +++
> > kernel/rcu/lazy-debug.h   | 154 +++++++++++++++++++++++++++
> > kernel/rcu/rcu.h          |   8 ++
> > kernel/rcu/rcuscale.c     |  70 +++++++++++-
> > kernel/rcu/rcutorture.c   |  16 +--
> > kernel/rcu/sync.c         |   2 +-
> > kernel/rcu/tiny.c         |   2 +-
> > kernel/rcu/tree.c         | 149 ++++++++++++++++++--------
> > kernel/rcu/tree.h         |  12 ++-
> > kernel/rcu/tree_exp.h     |   2 +-
> > kernel/rcu/tree_nocb.h    | 217 ++++++++++++++++++++++++++++++++------
> > kernel/workqueue.c        |   2 +-
> > lib/percpu-refcount.c     |   3 +-
> > net/rxrpc/conn_object.c   |   2 +-
> > 16 files changed, 565 insertions(+), 98 deletions(-)
> > create mode 100644 kernel/rcu/lazy-debug.h
> >
> > --
> > 2.38.0.413.g74048e4d9e-goog
> >