Commit 72c2075d authored by Alex Kogan's avatar Alex Kogan Committed by Xie XiuQi
Browse files

locking/qspinlock: Introduce CNA into the slow path of qspinlock

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). 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: default avatarAlex Kogan <alex.kogan@oracle.com>
Reviewed-by: default avatarSteve Sistare <steven.sistare@oracle.com>
Signed-off-by: default avatarWei Li <liwei391@huawei.com>
Reviewed-by: default avatarHanjun Guo <guohanjun@huawei.com>
Signed-off-by: default avatarYang Yingliang <yangyingliang@huawei.com>
parent 34b07a04
Loading
Loading
Loading
Loading
0% Loading or .
You are about to add 0 people to the discussion. Proceed with caution.
Please to comment