linux-kernel - Re: [PATCH v4 0/6] powerpc: queued spinlocks and rwlocks

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Date:   Fri, 24 Jul 2020 17:11:36 -0400
From:   Waiman Long <longman@...hat.com>
To:     Nicholas Piggin <npiggin@...il.com>, linuxppc-dev@...ts.ozlabs.org
Cc:     Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        Anton Blanchard <anton@...abs.org>,
        Michal Suchánek <msuchanek@...e.de>,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm-ppc@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: Re: [PATCH v4 0/6] powerpc: queued spinlocks and rwlocks

On 7/24/20 9:14 AM, Nicholas Piggin wrote:
> Updated with everybody's feedback (thanks all), and more performance
> results.
>
> What I've found is I might have been measuring the worst load point for
> the paravirt case, and by looking at a range of loads it's clear that
> queued spinlocks are overall better even on PV, doubly so when you look
> at the generally much improved worst case latencies.
>
> I have defaulted it to N even though I'm less concerned about the PV
> numbers now, just because I think it needs more stress testing. But
> it's very nicely selectable so should be low risk to include.
>
> All in all this is a very cool technology and great results especially
> on the big systems but even on smaller ones there are nice gains. Thanks
> Waiman and everyone who developed it.
>
> Thanks,
> Nick
>
> Nicholas Piggin (6):
>    powerpc/pseries: move some PAPR paravirt functions to their own file
>    powerpc: move spinlock implementation to simple_spinlock
>    powerpc/64s: implement queued spinlocks and rwlocks
>    powerpc/pseries: implement paravirt qspinlocks for SPLPAR
>    powerpc/qspinlock: optimised atomic_try_cmpxchg_lock that adds the
>      lock hint
>    powerpc: implement smp_cond_load_relaxed
>
>   arch/powerpc/Kconfig                          |  15 +
>   arch/powerpc/include/asm/Kbuild               |   1 +
>   arch/powerpc/include/asm/atomic.h             |  28 ++
>   arch/powerpc/include/asm/barrier.h            |  14 +
>   arch/powerpc/include/asm/paravirt.h           |  87 +++++
>   arch/powerpc/include/asm/qspinlock.h          |  91 ++++++
>   arch/powerpc/include/asm/qspinlock_paravirt.h |   7 +
>   arch/powerpc/include/asm/simple_spinlock.h    | 288 ++++++++++++++++
>   .../include/asm/simple_spinlock_types.h       |  21 ++
>   arch/powerpc/include/asm/spinlock.h           | 308 +-----------------
>   arch/powerpc/include/asm/spinlock_types.h     |  17 +-
>   arch/powerpc/lib/Makefile                     |   3 +
>   arch/powerpc/lib/locks.c                      |  12 +-
>   arch/powerpc/platforms/pseries/Kconfig        |   9 +-
>   arch/powerpc/platforms/pseries/setup.c        |   4 +-
>   include/asm-generic/qspinlock.h               |   4 +
>   16 files changed, 588 insertions(+), 321 deletions(-)
>   create mode 100644 arch/powerpc/include/asm/paravirt.h
>   create mode 100644 arch/powerpc/include/asm/qspinlock.h
>   create mode 100644 arch/powerpc/include/asm/qspinlock_paravirt.h
>   create mode 100644 arch/powerpc/include/asm/simple_spinlock.h
>   create mode 100644 arch/powerpc/include/asm/simple_spinlock_types.h
>
That patch series looks good to me. Thanks for working on this.

For the series,

Acked-by: Waiman Long <longman@...hat.com>