[v6,0/5] shoot lazy tlbs

Message

Nicholas Piggin Jan. 18, 2023, 8 a.m. UTC

It's time for that annual flamewar. Nothing really changed in core code
to clean things up or make it better for x86 last year, so I think we
can table that objection.

IIRC the situation left off with Andy proposing a different approach,
and Linus preferring to shoot the lazies at exit time (piggybacking on
the TLB flush IPI), which is what this series allows an arch to do.
Discussion thread here:

https://lore.kernel.org/linux-arch/[e-mail]/

I don't think there was any movement on this or other alternatives, or
code cleanups since then, but correct me if I'm wrong.

Since v5 of this series, there has just been a minor rebase to upstream,
and some tweaking of comments and code style. No functional changes.

Also included patch 5 which is the optimisation that combines final TLB
shootdown with the lazy tlb mm shootdown IPIs. Included because Linus
expected to see it. It works fine, but I have some other powerpc changes
I would like to go ahead of it so I would like to take those through the
powerpc tree. And actually giving it a release cycle without that
optimization will help stress test the final IPI cleanup path too, which
I would like.

Even without the last patch, the additional IPIs caused by shoot lazy
is down in the noise so I'm not too concerned about it.

Thanks,
Nick

Nicholas Piggin (5):
  lazy tlb: introduce lazy tlb mm refcount helper functions
  lazy tlb: allow lazy tlb mm refcounting to be configurable
  lazy tlb: shoot lazies, non-refcounting lazy tlb mm reference handling
    scheme
  powerpc/64s: enable MMU_LAZY_TLB_SHOOTDOWN
  powerpc/64s/radix: combine final TLB flush and lazy tlb mm shootdown
    IPIs

 Documentation/mm/active_mm.rst       |  6 +++
 arch/Kconfig                         | 32 ++++++++++++++
 arch/arm/mach-rpc/ecard.c            |  2 +-
 arch/powerpc/Kconfig                 |  1 +
 arch/powerpc/kernel/smp.c            |  2 +-
 arch/powerpc/mm/book3s64/radix_tlb.c | 30 +++++++++++--
 fs/exec.c                            |  2 +-
 include/linux/sched/mm.h             | 28 ++++++++++++
 kernel/cpu.c                         |  2 +-
 kernel/exit.c                        |  2 +-
 kernel/fork.c                        | 65 ++++++++++++++++++++++++++++
 kernel/kthread.c                     | 21 +++++----
 kernel/sched/core.c                  | 35 ++++++++++-----
 kernel/sched/sched.h                 |  4 +-
 14 files changed, 205 insertions(+), 27 deletions(-)