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/ 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 ] [ debug code for detecting "wake" in kernel's call_rcu() callbacks. ] The following 2 scripts can be used to check if any callbacks in the kernel are doing a wake up (it is best effort and may miss some things, but we found issues using it) 1. Script to search for call_rcu() references and dump the callback list to a file: #!/bin/bash rm func-list touch func-list for f in $(find . \( -name "*.c" -o -name "*.h" \) | grep -v rcu); do funcs=$(perl -0777 -ne 'while(m/call_rcu\([&]?.+,\s?(.+)\).*;/g){print "$1\n";}' $f) if [ "x$funcs" != "x" ]; then for func in $funcs; do echo "$f $func" >> func-list echo "$f $func" done fi done cat func-list | sort | uniq | tee func-list-sorted 2. Script to search "wake" after callback references: #!/bin/bash while read fl; do file=$(echo $fl | cut -d " " -f1) func=$(echo $fl | cut -d " " -f2) grep -A 30 $func $file | grep wake > /dev/null if [ $? -eq 0 ]; then echo "keyword wake found after function reference $func in $file" echo "Output:" grep -A 30 $func $file echo "===========================================================" fi done < func-list-sorted 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
