[PATCH v5 0/6] powerPC/pSeries use pv-qpsinlock as the default spinlock implemention

From: Pan Xinhui
Date: Thu Jun 02 2016 - 05:24:27 EST

From: root <root@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>

change from v4:
BUG FIX. thanks boqun reporting this issue.
struct __qspinlock has different layout in bigendian mahcine.
native_queued_spin_unlock() may write value to a wrong address. now fix it.

change from v3:
a big change in [PATCH v4 4/6] pv-qspinlock: powerpc support pv-qspinlock
no other patch changed.
and the patch cover letter tilte has changed as only pseries may need use pv-qspinlock, not all powerpc.

1) __pv_wait will not return until *ptr != val as Waiman gives me a tip.
2) support lock holder serching by storing cpu number into a hash table(implemented as an array)
This is because lock_stealing hit too much, up to 10%~20% of all the successful lock(), and avoid
vcpu slices bounce.

change from v2:
__spin_yeild_cpu() will yield slices to lpar if target cpu is running.
remove unnecessary rmb() in __spin_yield/wake_cpu.
__pv_wait() will check the *ptr == val.
some commit message change

change fome v1:
separate into 6 pathes from one patch
some minor code changes.

I do several tests on pseries IBM,8408-E8E with 32cpus, 64GB memory, kernel 4.6
benchmark test results are below.

2 perf tests:
perf bench futex hash
perf bench futex lock-pi

|futex hash | 528572 ops | 573238 ops |
|futex lock-pi | 354 ops | 352 ops |

scheduler test:
Test how many loops of schedule() can finish within 10 seconds on all cpus.

|schedule() loops| 340890082 | 331730973 |

kernel compiling test:
build a default linux kernel image to see how long it took

| compiling takes| 22m | 22m |

some notes:
the performace is as good as current spinlock's. in some case better while some cases worse.
But in some other tests(not listed here), we verify the two spinlock's workloads by perf record&report.
pv-qspinlock is light-weight than current spinlock.
This patch series depends on 2 patches:
[patch]powerpc: Implement {cmp}xchg for u8 and u16
[patch]locking/pvqspinlock: Add lock holder CPU argument to pv_wait() from Waiman

Some other patches in Waiman's "locking/pvqspinlock: Fix missed PV wakeup & support PPC" are not applied for now.

Pan Xinhui (6):
qspinlock: powerpc support qspinlock
powerpc: pseries/Kconfig: Add qspinlock build config
powerpc: lib/locks.c: Add cpu yield/wake helper function
pv-qspinlock: powerpc support pv-qspinlock
pv-qspinlock: use cmpxchg_release in __pv_queued_spin_unlock
powerpc: pseries: Add pv-qspinlock build config/make

arch/powerpc/include/asm/qspinlock.h | 41 +++++++
arch/powerpc/include/asm/qspinlock_paravirt.h | 38 +++++++
.../powerpc/include/asm/qspinlock_paravirt_types.h | 13 +++
arch/powerpc/include/asm/spinlock.h | 31 ++++--
arch/powerpc/include/asm/spinlock_types.h | 4 +
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/paravirt.c | 121 +++++++++++++++++++++
arch/powerpc/lib/locks.c | 37 +++++++
arch/powerpc/platforms/pseries/Kconfig | 9 ++
arch/powerpc/platforms/pseries/setup.c | 5 +
kernel/locking/qspinlock_paravirt.h | 2 +-
11 files changed, 289 insertions(+), 13 deletions(-)
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/qspinlock_paravirt_types.h
create mode 100644 arch/powerpc/kernel/paravirt.c