On 9/15/20 2:05 PM, Alex Kogan wrote:
In CNA, spinning threads are organized in two queues, a primary queue for
threads running on the same node as the current lock holder, and a
secondary queue for threads running on other nodes. After acquiring the
MCS lock and before acquiring the spinlock, the MCS lock
holder checks whether the next waiter in the primary queue (if exists) is
running on the same NUMA node. If it is not, that waiter is detached from
the main queue and moved into the tail of the secondary queue. This way,
we gradually filter the primary queue, leaving only waiters running on
the same preferred NUMA node. For more details, see
https://arxiv.org/abs/1810.05600.
Note that this variant of CNA may introduce starvation by continuously
passing the lock between waiters in the main queue. This issue will be
addressed later in the series.
Enabling CNA is controlled via a new configuration option
(NUMA_AWARE_SPINLOCKS). By default, the CNA variant is patched in at the
boot time only if we run on a multi-node machine in native environment and
the new config is enabled. (For the time being, the patching requires
CONFIG_PARAVIRT_SPINLOCKS to be enabled as well. However, this should be
resolved once static_call() is available.) This default behavior can be
overridden with the new kernel boot command-line option
"numa_spinlock=on/off" (default is "auto").
Signed-off-by: Alex Kogan <alex.ko...@oracle.com>
Reviewed-by: Steve Sistare <steven.sist...@oracle.com>
Reviewed-by: Waiman Long <long...@redhat.com>
---
.../admin-guide/kernel-parameters.txt | 10 +
arch/x86/Kconfig | 20 ++
arch/x86/include/asm/qspinlock.h | 4 +
arch/x86/kernel/alternative.c | 4 +
kernel/locking/mcs_spinlock.h | 2 +-
kernel/locking/qspinlock.c | 42 ++-
kernel/locking/qspinlock_cna.h | 336 ++++++++++++++++++
7 files changed, 413 insertions(+), 5 deletions(-)
create mode 100644 kernel/locking/qspinlock_cna.h
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index a1068742a6df..51ce050f8701 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3353,6 +3353,16 @@
nox2apic [X86-64,APIC] Do not enable x2APIC mode.
+ 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.
+ off - Unconditionally disable this variant.
+
+ Not specifying this option is equivalent to
+ numa_spinlock=auto.
+
cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
Some features depend on CPU0. Known dependencies are:
You will have to move down this hunk according to alphabetic order.
Other than that this patch looks good to me.
Cheers,
Longman
