|From:||Waiman Long <Waiman.Long@hp.com>|
|To:||Thomas Gleixner <email@example.com>, Ingo Molnar <firstname.lastname@example.org>, "H. Peter Anvin" <email@example.com>, Peter Zijlstra <firstname.lastname@example.org>|
|Subject:||[PATCH v10 00/19] qspinlock: a 4-byte queue spinlock with PV support|
|Date:||Wed, 7 May 2014 11:01:28 -0400|
|Cc:||email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, Paolo Bonzini <email@example.com>, Konrad Rzeszutek Wilk <firstname.lastname@example.org>, Boris Ostrovsky <email@example.com>, "Paul E. McKenney" <firstname.lastname@example.org>, Rik van Riel <email@example.com>, Linus Torvalds <firstname.lastname@example.org>, Raghavendra K T <email@example.com>, David Vrabel <firstname.lastname@example.org>, Oleg Nesterov <email@example.com>, Gleb Natapov <firstname.lastname@example.org>, Scott J Norton <email@example.com>, Chegu Vinod <firstname.lastname@example.org>, Waiman Long <Waiman.Long@hp.com>|
v9->v10: - Make some minor changes to qspinlock.c to accommodate review feedback. - Change author to PeterZ for 2 of the patches. - Include Raghavendra KT's test results in patch 18. v8->v9: - Integrate PeterZ's version of the queue spinlock patch with some modification: http://lkml.kernel.org/r/20140310154236.038181843@infrade... - Break the more complex patches into smaller ones to ease review effort. - Fix a racing condition in the PV qspinlock code. v7->v8: - Remove one unneeded atomic operation from the slowpath, thus improving performance. - Simplify some of the codes and add more comments. - Test for X86_FEATURE_HYPERVISOR CPU feature bit to enable/disable unfair lock. - Reduce unfair lock slowpath lock stealing frequency depending on its distance from the queue head. - Add performance data for IvyBridge-EX CPU. v6->v7: - Remove an atomic operation from the 2-task contending code - Shorten the names of some macros - Make the queue waiter to attempt to steal lock when unfair lock is enabled. - Remove lock holder kick from the PV code and fix a race condition - Run the unfair lock & PV code on overcommitted KVM guests to collect performance data. v5->v6: - Change the optimized 2-task contending code to make it fairer at the expense of a bit of performance. - Add a patch to support unfair queue spinlock for Xen. - Modify the PV qspinlock code to follow what was done in the PV ticketlock. - Add performance data for the unfair lock as well as the PV support code. v4->v5: - Move the optimized 2-task contending code to the generic file to enable more architectures to use it without code duplication. - Address some of the style-related comments by PeterZ. - Allow the use of unfair queue spinlock in a real para-virtualized execution environment. - Add para-virtualization support to the qspinlock code by ensuring that the lock holder and queue head stay alive as much as possible. v3->v4: - Remove debugging code and fix a configuration error - Simplify the qspinlock structure and streamline the code to make it perform a bit better - Add an x86 version of asm/qspinlock.h for holding x86 specific optimization. - Add an optimized x86 code path for 2 contending tasks to improve low contention performance. v2->v3: - Simplify the code by using numerous mode only without an unfair option. - Use the latest smp_load_acquire()/smp_store_release() barriers. - Move the queue spinlock code to kernel/locking. - Make the use of queue spinlock the default for x86-64 without user configuration. - Additional performance tuning. 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 has 3 different sections: 1) Patches 1-7: Introduces a queue-based spinlock implementation that can 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 break data alignments. 2) Patches 8-13: Enables the use of unfair queue spinlock in a virtual guest. This can resolve some of the locking related performance issues due to the fact that the next CPU to get the lock may have been scheduled out for a period of time. 3) Patches 14-19: Enable qspinlock para-virtualization support by halting the waiting CPUs after spinning for a certain amount of time. The unlock code will detect the a sleeping waiter and wake it up. This is essentially the same logic as the PV ticketlock code. The queue spinlock has slightly better performance than the ticket spinlock in uncontended case. Its performance can be much better with moderate to heavy contention. 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. 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. Peter Zijlstra (2): qspinlock: Add pending bit qspinlock: Optimize for smaller NR_CPUS Waiman Long (17): qspinlock: A simple generic 4-byte queue spinlock qspinlock, x86: Enable x86-64 to use queue spinlock qspinlock: Extract out the exchange of tail code word qspinlock: prolong the stay in the pending bit path qspinlock: Use a simple write to grab the lock, if applicable qspinlock: Make a new qnode structure to support virtualization qspinlock: Prepare for unfair lock support qspinlock, x86: Allow unfair spinlock in a virtual guest qspinlock: Split the MCS queuing code into a separate slowerpath unfair qspinlock: Variable frequency lock stealing mechanism unfair qspinlock: Enable lock stealing in lock waiters pvqspinlock, x86: Rename paravirt_ticketlocks_enabled pvqspinlock, x86: Add PV data structure & methods pvqspinlock: Enable coexistence with the unfair lock pvqspinlock: Add qspinlock para-virtualization support pvqspinlock, x86: Enable PV qspinlock PV for KVM pvqspinlock, x86: Enable PV qspinlock for XEN arch/x86/Kconfig | 12 + arch/x86/include/asm/paravirt.h | 18 +- arch/x86/include/asm/paravirt_types.h | 17 + arch/x86/include/asm/pvqspinlock.h | 306 +++++++++++ arch/x86/include/asm/qspinlock.h | 141 +++++ arch/x86/include/asm/spinlock.h | 9 +- arch/x86/include/asm/spinlock_types.h | 4 + arch/x86/kernel/Makefile | 1 + arch/x86/kernel/kvm.c | 137 +++++- arch/x86/kernel/paravirt-spinlocks.c | 36 ++- arch/x86/xen/spinlock.c | 149 +++++- include/asm-generic/qspinlock.h | 118 +++++ include/asm-generic/qspinlock_types.h | 82 +++ kernel/Kconfig.locks | 7 + kernel/locking/Makefile | 1 + kernel/locking/mcs_spinlock.h | 1 + kernel/locking/qspinlock.c | 918 +++++++++++++++++++++++++++++++++ 17 files changed, 1945 insertions(+), 12 deletions(-) create mode 100644 arch/x86/include/asm/pvqspinlock.h create mode 100644 arch/x86/include/asm/qspinlock.h create mode 100644 include/asm-generic/qspinlock.h create mode 100644 include/asm-generic/qspinlock_types.h create mode 100644 kernel/locking/qspinlock.c -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to email@example.com More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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