[ Based on recent discussion with Linus, it appears that this series just proves that it's time to get rid of active mm altogether:
https://lore.kernel.org/lkml/CAHk-=wgztWbA4z85xKob4eS9P=Nt5h4j=hnn+pc90expski...@mail.gmail.com/ I'm posting a v2 fixing minor issues from v1 in case it can be useful to try hazard pointers with other use-cases, or for further benchmarking of active mm tracking impact. ] Hazard pointers appear to be a good fit for replacing refcount based lazy active mm tracking. Highlight: will-it-scale context_switch1_threads nr threads (-t) speedup 1 -0.2% 2 +0.4% 3 +0.2% 6 +0.6% 12 +0.8% 24 +3% 48 +12% 96 +21% 192 +28% 384 +4% 768 -0.6% This series applies on top of v6.11.1. Signed-off-by: Mathieu Desnoyers <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Nicholas Piggin <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: Will Deacon <[email protected]> Cc: Alan Stern <[email protected]> Cc: John Stultz <[email protected]> Cc: Neeraj Upadhyay <[email protected]> Cc: Boqun Feng <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Joel Fernandes <[email protected]> Cc: Josh Triplett <[email protected]> Cc: Uladzislau Rezki <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Lai Jiangshan <[email protected]> Cc: Zqiang <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Waiman Long <[email protected]> Cc: Mark Rutland <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: [email protected] Cc: Mateusz Guzik <[email protected]> Cc: Jonas Oberhauser <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Mathieu Desnoyers (4): compiler.h: Introduce ptr_eq() to preserve address dependency Documentation: RCU: Refer to ptr_eq() hp: Implement Hazard Pointers sched+mm: Use hazard pointers to track lazy active mm existence Documentation/RCU/rcu_dereference.rst | 38 ++++++- Documentation/mm/active_mm.rst | 9 +- arch/Kconfig | 32 ------ arch/powerpc/Kconfig | 1 - arch/powerpc/mm/book3s64/radix_tlb.c | 23 +--- include/linux/compiler.h | 63 ++++++++++ include/linux/hp.h | 158 ++++++++++++++++++++++++++ include/linux/mm_types.h | 3 - include/linux/sched/mm.h | 71 +++++------- kernel/Makefile | 2 +- kernel/exit.c | 4 +- kernel/fork.c | 47 ++------ kernel/hp.c | 46 ++++++++ kernel/sched/sched.h | 8 +- lib/Kconfig.debug | 10 -- 15 files changed, 350 insertions(+), 165 deletions(-) create mode 100644 include/linux/hp.h create mode 100644 kernel/hp.c -- 2.39.2
