The qspinlock conversion resulted in some latency regressions particularly in the paravirt (SPLPAR) case. I haven't been able to improve them much so for now I rewrite with a different paravirt algorithm (as s390 does). This isn't the same as s390 but they have some of the same concerns by the looks, so possibly if we can't unify with generic code we could unify with them at some point.
Thanks, Nick Nicholas Piggin (14): powerpc/qspinlock: powerpc qspinlock implementation powerpc/qspinlock: add mcs queueing for contended waiters powerpc/qspinlock: use a half-word store to unlock to avoid larx/stcx. powerpc/qspinlock: convert atomic operations to assembly powerpc/qspinlock: allow new waiters to steal the lock before queueing powerpc/qspinlock: theft prevention to control latency powerpc/qspinlock: store owner CPU in lock word powerpc/qspinlock: paravirt yield to lock owner powerpc/qspinlock: implement option to yield to previous node powerpc/qspinlock: allow stealing when head of queue yields powerpc/qspinlock: allow propagation of yield CPU down the queue powerpc/qspinlock: add ability to prod new queue head CPU powerpc/qspinlock: trylock and initial lock attempt may steal powerpc/qspinlock: use spin_begin/end API arch/powerpc/Kconfig | 1 - arch/powerpc/include/asm/qspinlock.h | 130 ++-- arch/powerpc/include/asm/qspinlock_types.h | 65 ++ arch/powerpc/include/asm/spinlock_types.h | 2 +- arch/powerpc/lib/Makefile | 4 +- arch/powerpc/lib/qspinlock.c | 671 +++++++++++++++++++++ 6 files changed, 829 insertions(+), 44 deletions(-) create mode 100644 arch/powerpc/include/asm/qspinlock_types.h create mode 100644 arch/powerpc/lib/qspinlock.c -- 2.35.1
