On Thu, Sep 23, 2021 at 3:26 AM Davidlohr Bueso <dave@xxxxxxxxxxxx> wrote: > > 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. I hope we shouldn't force disable it in the Kconfig. Could we put this idea in numa_spinlock=auto? > > Thanks, > Davidlohr -- Best Regards Guo Ren
