On Thu, Jul 09, 2020 at 08:20:25PM +1000, Michael Ellerman wrote:

Nicholas Piggin [off-list ref] writes:

quoted

These have shown significantly improved performance and fairness when
spinlock contention is moderate to high on very large systems.

 [ Numbers hopefully forthcoming after more testing, but initial
   results look good ]

Would be good to have something here, even if it's preliminary.

quoted

Thanks to the fast path, single threaded performance is not noticably
hurt.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/Kconfig                      | 13 ++++++++++++
 arch/powerpc/include/asm/Kbuild           |  2 ++
 arch/powerpc/include/asm/qspinlock.h      | 25 +++++++++++++++++++++++
 arch/powerpc/include/asm/spinlock.h       |  5 +++++
 arch/powerpc/include/asm/spinlock_types.h |  5 +++++
 arch/powerpc/lib/Makefile                 |  3 +++

quoted

 include/asm-generic/qspinlock.h           |  2 ++

Who's ack do we need for that part?

Mine I suppose would do, as discussed earlier, it probably isn't
required anymore, but I understand the paranoia of not wanting to change
too many things at once :-)


Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>