diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2022-11-26 19:59:27 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2022-12-02 17:48:50 +1100 |
| commit | f61ab43cc1a6146d6eef7e0713a452c3677ad13e (patch) | |
| tree | 5c492373691342daebbb8422523b23aed23a3171 /arch/powerpc/lib | |
| parent | be742c573fdafcfa1752642ca1c7aaf08c258128 (diff) | |
| download | linux-f61ab43cc1a6146d6eef7e0713a452c3677ad13e.tar.bz2 | |
powerpc/qspinlock: allow lock stealing in trylock and lock fastpath
This change allows trylock to steal the lock. It also allows the initial
lock attempt to steal the lock rather than bailing out and going to the
slow path.
This gives trylock more strength: without this a continually-contended
lock will never permit a trylock to succeed. With this change, the
trylock has a small but non-zero chance.
It also gives the lock fastpath most of the benefit of passing the
reservation back through to the steal loop in the slow path without the
complexity.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221126095932.1234527-13-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/lib')
| -rw-r--r-- | arch/powerpc/lib/qspinlock.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/powerpc/lib/qspinlock.c b/arch/powerpc/lib/qspinlock.c index 2f6c0bed25ea..8e5b8bc3f094 100644 --- a/arch/powerpc/lib/qspinlock.c +++ b/arch/powerpc/lib/qspinlock.c @@ -24,7 +24,11 @@ struct qnodes { /* Tuning parameters */ static int steal_spins __read_mostly = (1 << 5); +#if _Q_SPIN_TRY_LOCK_STEAL == 1 +static const bool maybe_stealers = true; +#else static bool maybe_stealers __read_mostly = true; +#endif static int head_spins __read_mostly = (1 << 8); static bool pv_yield_owner __read_mostly = true; @@ -483,6 +487,10 @@ void pv_spinlocks_init(void) #include <linux/debugfs.h> static int steal_spins_set(void *data, u64 val) { +#if _Q_SPIN_TRY_LOCK_STEAL == 1 + /* MAYBE_STEAL remains true */ + steal_spins = val; +#else static DEFINE_MUTEX(lock); /* @@ -507,6 +515,7 @@ static int steal_spins_set(void *data, u64 val) steal_spins = val; } mutex_unlock(&lock); +#endif return 0; } |