v1->v2: - Add some more comments to document what the code does. - Add a numerous CPU mode to support >= 16K CPUs - Add a configuration option to allow lock stealing which can further improve performance in many cases. - Enable wakeup of queue head CPU at unlock time for non-numerous CPU mode. This patch set introduces a queue-based spinlock implementation that can be used to replace the default ticket spinlock without increasing the size of the spinlock data structure. As a result, critical kernel data structures that embed spinlock won't increase in size and breaking data alignments. The queue spinlock has about the same performance as the ticket spinlock in uncontended case. Its performance is better with moderate to heavy contention. It may be slightly slower in light to moderate level of lock contention where the queue depth is around 1-2. This patch has the potential of improving the performance of all the workloads that have moderate to heavy spinlock contention. The queue spinlock is especially suitable for NUMA machines with at least 2 sockets, though noticeable performance benefit probably won't show up in machines with less than 4 sockets. There is also an experimental option to allow lock stealing thus breaking the FIFO guarantee of lock acquisition. However, performance usually goes up with an unfair lock. The purpose of this patch set is not to solve any particular spinlock contention problems. Those need to be solved by refactoring the code to make more efficient use of the lock or finer granularity ones. The main purpose is to make the lock contention problems more tolerable until someone can spend the time and effort to fix them. Signed-off-by: Waiman Long <Waiman.Long@xxxxxx> Waiman Long (2): qspinlock: Introducing a 4-byte queue spinlock implementation qspinlock x86: Enable x86 to use queue spinlock arch/x86/Kconfig | 3 + arch/x86/include/asm/spinlock.h | 2 + arch/x86/include/asm/spinlock_types.h | 4 + arch/x86/kernel/paravirt-spinlocks.c | 10 + include/asm-generic/qspinlock.h | 207 +++++++++++++ lib/Kconfig | 25 ++ lib/Makefile | 1 + lib/qspinlock.c | 522 +++++++++++++++++++++++++++++++++ 8 files changed, 774 insertions(+), 0 deletions(-) create mode 100644 include/asm-generic/qspinlock.h create mode 100644 lib/qspinlock.c -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
