On Tue, Oct 04, 2022 at 02:41:46AM +0000, Joel Fernandes (Google) wrote: > 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 ] Thank you for your continued work on this! I pulled these into an experimental branch, applied Uladzislau's Tested-by and ran a quick round of rcutorture. >From TREE02, TREE03, and TREE09 I got this: In file included from kernel/rcu/tree.c:68: kernel/rcu/tree.h:449:13: error: ‘wake_nocb_gp’ used but never defined [-Werror] 449 | static bool wake_nocb_gp(struct rcu_data *rdp, bool force); | ^~~~~~~~~~~~ One could argue that this is not a big deal, except that Linus gets a bit tetchy when this sort of thing shows up in mainline. Nevetheless, it looks like we might be getting quite close! Thanx, Paul > 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 >
