diff options
| author | Waiman Long <Waiman.Long@hp.com> | 2014-02-03 13:18:49 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2014-06-06 07:58:28 +0200 |
| commit | 70af2f8a4f48d6cebdf92d533d3aef37853ce6de (patch) | |
| tree | 2a8d7b54053ef9fc7d45794ab28addbd00870819 /kernel/Kconfig.locks | |
| parent | 9161f5409798d52aa8598ff12575fde2327bed84 (diff) | |
| download | lwn-70af2f8a4f48d6cebdf92d533d3aef37853ce6de.tar.gz lwn-70af2f8a4f48d6cebdf92d533d3aef37853ce6de.zip | |
locking/rwlocks: Introduce 'qrwlocks' - fair, queued rwlocks
This rwlock uses the arch_spin_lock_t as a waitqueue, and assuming the
arch_spin_lock_t is a fair lock (ticket,mcs etc..) the resulting
rwlock is a fair lock.
It fits in the same 8 bytes as the regular rwlock_t by folding the
reader and writer count into a single integer, using the remaining 4
bytes for the arch_spinlock_t.
Architectures that can single-copy adress bytes can optimize
queue_write_unlock() with a 0 write to the LSB (the write count).
Performance as measured by Davidlohr Bueso (rwlock_t -> qrwlock_t):
+--------------+-------------+---------------+
| Workload | #users | delta |
+--------------+-------------+---------------+
| alltests | > 1400 | -4.83% |
| custom | 0-100,> 100 | +1.43%,-1.57% |
| high_systime | > 1000 | -2.61 |
| shared | all | +0.32 |
+--------------+-------------+---------------+
http://www.stgolabs.net/qrwlock-stuff/aim7-results-vs-rwsem_optsin/
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
[peterz: near complete rewrite]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Paul E.McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/n/tip-gac1nnl3wvs2ij87zv2xkdzq@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/Kconfig.locks')
| -rw-r--r-- | kernel/Kconfig.locks | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks index d2b32ac27a39..35536d9c0964 100644 --- a/kernel/Kconfig.locks +++ b/kernel/Kconfig.locks @@ -223,3 +223,10 @@ endif config MUTEX_SPIN_ON_OWNER def_bool y depends on SMP && !DEBUG_MUTEXES + +config ARCH_USE_QUEUE_RWLOCK + bool + +config QUEUE_RWLOCK + def_bool y if ARCH_USE_QUEUE_RWLOCK + depends on SMP |