On Fri, 14 May 2021, Alex Kogan wrote:
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a816935d23d4..94d35507560c 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3515,6 +3515,16 @@ NUMA balancing. Allowed values are enable and disable + numa_spinlock= [NUMA, PV_OPS] Select the NUMA-aware variant + of spinlock. The options are: + auto - Enable this variant if running on a multi-node + machine in native environment. + on - Unconditionally enable this variant.
Is there any reason why the user would explicitly pass the on option when the auto thing already does the multi-node check? Perhaps strange numa topologies? Otherwise I would say it's not needed and the fewer options we give the user for low level locking the better.
+ off - Unconditionally disable this variant. + + Not specifying this option is equivalent to + numa_spinlock=auto. + numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 'node', 'default' can be specified This can be set from sysctl after boot. diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 0045e1b44190..819c3dad8afc 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1564,6 +1564,26 @@ config NUMA Otherwise, you should say N. +config NUMA_AWARE_SPINLOCKS + bool "Numa-aware spinlocks" + depends on NUMA + depends on QUEUED_SPINLOCKS + depends on 64BIT + # For now, we depend on PARAVIRT_SPINLOCKS to make the patching work. + # This is awkward, but hopefully would be resolved once static_call() + # is available. + depends on PARAVIRT_SPINLOCKS
We now have static_call() - see 9183c3f9ed7.
+ default y + help + Introduce NUMA (Non Uniform Memory Access) awareness into + the slow path of spinlocks. + + In this variant of qspinlock, the kernel will try to keep the lock + on the same node, thus reducing the number of remote cache misses, + while trading some of the short term fairness for better performance. + + Say N if you want absolute first come first serve fairness.
This would also need a depends on !PREEMPT_RT, no? Raw spinlocks really want the determinism. Thanks, Davidlohr
