hulk inclusion
category: feature
bugzilla: 13227
CVE: NA

-------------------------------------------------

In CNA, 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. At the unlock time,
the lock holder scans the main queue looking for a thread running on
the same node. 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, and the lock is passed to T. If such T is not found, the
lock is passed to the first node in the secondary queue. Finally, if the
secondary queue is empty, the lock is passed to the next thread in the
main queue. For more details, see https://arxiv.org/abs/1810.05600.

Note that this variant of CNA may introduce starvation by continuously
passing the lock to threads running on the same node. This issue
will be addressed later in the series.

Enabling CNA is controlled via a new configuration option
(NUMA_AWARE_SPINLOCKS). The CNA variant is patched in
at the boot time only if we run a multi-node machine, 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.
Signed-off-by: NAlex Kogan <alex.kogan@oracle.com>
Reviewed-by: NSteve Sistare <steven.sistare@oracle.com>
Signed-off-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>