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/ > > 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 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. 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 >
