Hi Will/Catalin, On Wed, Jan 08, 2020 at 05:09:05AM +0000, Shijith Thotton wrote: > On Mon, Dec 30, 2019 at 02:40:37PM -0500, Alex Kogan wrote: > > Minor changes from v7 based on feedback from Longman: > > ----------------------------------------------------- > > > > - Move __init functions from alternative.c to qspinlock_cna.h > > > > - Introduce enum for return values from cna_pre_scan(), for better > > readability. > > > > - Add/revise a few comments to improve readability. > > > > > > Summary > > ------- > > > > Lock throughput can be increased by handing a lock to a waiter on the > > same NUMA node as the lock holder, provided care is taken to avoid > > starvation of waiters on other NUMA nodes. This patch introduces CNA > > (compact NUMA-aware lock) as the slow path for qspinlock. It is > > enabled through a configuration option (NUMA_AWARE_SPINLOCKS). > > > > CNA is a NUMA-aware version of the MCS lock. Spinning threads are > > organized in two queues, a main queue for threads running on the same > > node as the current lock holder, and a secondary queue for threads > > running on other nodes. Threads store the ID of the node on which > > they are running in their queue nodes. After acquiring the MCS lock and > > before acquiring the spinlock, the lock holder scans the main queue > > looking for a thread running on the same node (pre-scan). If found (call > > it thread T), all threads in the main queue between the current lock > > holder and T are moved to the end of the secondary queue. If such T > > is not found, we make another scan of the main queue after acquiring > > the spinlock when unlocking the MCS lock (post-scan), starting at the > > node where pre-scan stopped. If both scans fail to find such T, the > > MCS lock is passed to the first thread in the secondary queue. If the > > secondary queue is empty, the MCS lock is passed to the next thread in the > > main queue. To avoid starvation of threads in the secondary queue, those > > threads are moved back to the head of the main queue after a certain > > number of intra-node lock hand-offs. > > > > More details are available at https://urldefense.proofpoint.com/v2/url?u=https-3A__arxiv.org_abs_1810.05600&d=DwIDAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=G9w4KsPaQLACBfGCL35PtiRH996yqJDxAZwrWegU2qQ&m=AoOLTQlgNjtdBvY_yWd6ViBXrVM6o2wqXOdFA4B_F2A&s=yUjG9gfi3BtLKDEjgki86h52GVXMvDQ6ZClMvoIG034&e= . > > > > The series applies on top of v5.5.0-rc2, commit ea200dec51. > > Performance numbers are available in previous revisions > > of the series. > > > > Further comments are welcome and appreciated. > > > > Alex Kogan (5): > > locking/qspinlock: Rename mcs lock/unlock macros and make them more > > generic > > locking/qspinlock: Refactor the qspinlock slow path > > locking/qspinlock: Introduce CNA into the slow path of qspinlock > > locking/qspinlock: Introduce starvation avoidance into CNA > > locking/qspinlock: Introduce the shuffle reduction optimization into > > CNA > > > > .../admin-guide/kernel-parameters.txt | 18 + > > arch/arm/include/asm/mcs_spinlock.h | 6 +- > > arch/x86/Kconfig | 20 + > > arch/x86/include/asm/qspinlock.h | 4 + > > arch/x86/kernel/alternative.c | 4 + > > include/asm-generic/mcs_spinlock.h | 4 +- > > kernel/locking/mcs_spinlock.h | 20 +- > > kernel/locking/qspinlock.c | 82 +++- > > kernel/locking/qspinlock_cna.h | 400 ++++++++++++++++++ > > kernel/locking/qspinlock_paravirt.h | 2 +- > > 10 files changed, 537 insertions(+), 23 deletions(-) > > create mode 100644 kernel/locking/qspinlock_cna.h > > > > -- > > 2.21.0 (Apple Git-122.2) > > > > Tried out queued spinlock slowpath improvements on arm64 (ThunderX2) by > hardwiring CNA APIs to queued_spin_lock_slowpath() and numbers are pretty > good with the CNA changes. > > Speed-up on v5.5-rc4 kernel: > > will-it-scale/open1_threads: > #thr speed-up > 1 1.00 > 2 0.97 > 4 0.98 > 8 1.02 > 16 0.95 > 32 1.63 > 64 1.70 > 128 2.09 > 224 2.16 > > will-it-scale/lock2_threads: > #thr speed-up > 1 0.98 > 2 0.99 > 4 0.90 > 8 0.98 > 16 0.99 > 32 1.52 > 64 2.31 > 128 2.25 > 224 2.04 > > #thr - number of threads > speed-up - number with CNA patch / number with stock kernel > > Please share your thoughts on best way to enable this series on arm64. Please comment if you got a chance to look at this. Thanks, Shijith
