From: Alex Kogan <alex.kogan@oracle.com>
To: linux@armlinux.org.uk, peterz@infradead.org, mingo@redhat.com,
will.deacon@arm.com, arnd@arndb.de, longman@redhat.com,
linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de,
hpa@zytor.com, x86@kernel.org, guohanjun@huawei.com,
jglauber@marvell.com
Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
alex.kogan@oracle.com, dave.dice@oracle.com
Subject: [PATCH v14 5/6] locking/qspinlock: Avoid moving certain threads between waiting queues in CNA
Date: Thu, 1 Apr 2021 11:31:55 -0400 [thread overview]
Message-ID: <20210401153156.1165900-6-alex.kogan@oracle.com> (raw)
In-Reply-To: <20210401153156.1165900-1-alex.kogan@oracle.com>
Prohibit moving certain threads (e.g., in irq and nmi contexts)
to the secondary queue. Those prioritized threads will always stay
in the primary queue, and so will have a shorter wait time for the lock.
Signed-off-by: Alex Kogan <alex.kogan@oracle.com>
Reviewed-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Waiman Long <longman@redhat.com>
---
kernel/locking/qspinlock_cna.h | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)
diff --git a/kernel/locking/qspinlock_cna.h b/kernel/locking/qspinlock_cna.h
index 0513360c11fe..29c3abbd3d94 100644
--- a/kernel/locking/qspinlock_cna.h
+++ b/kernel/locking/qspinlock_cna.h
@@ -4,6 +4,7 @@
#endif
#include <linux/topology.h>
+#include <linux/sched/rt.h>
/*
* Implement a NUMA-aware version of MCS (aka CNA, or compact NUMA-aware lock).
@@ -35,7 +36,8 @@
* 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.
+ * preferred NUMA node. Note that certain priortized waiters (e.g., in
+ * irq and nmi contexts) are excluded from being moved to the secondary queue.
*
* We change the NUMA node preference after a waiter at the head of the
* secondary queue spins for a certain amount of time (10ms, by default).
@@ -49,6 +51,8 @@
* Dave Dice <dave.dice@oracle.com>
*/
+#define CNA_PRIORITY_NODE 0xffff
+
struct cna_node {
struct mcs_spinlock mcs;
u16 numa_node;
@@ -121,9 +125,10 @@ static int __init cna_init_nodes(void)
static __always_inline void cna_init_node(struct mcs_spinlock *node)
{
+ bool priority = !in_task() || irqs_disabled() || rt_task(current);
struct cna_node *cn = (struct cna_node *)node;
- cn->numa_node = cn->real_numa_node;
+ cn->numa_node = priority ? CNA_PRIORITY_NODE : cn->real_numa_node;
cn->partial_order = LOCAL_WAITER_FOUND;
cn->start_time = 0;
}
@@ -266,11 +271,13 @@ static void cna_order_queue(struct mcs_spinlock *node)
next_numa_node = ((struct cna_node *)next)->numa_node;
if (next_numa_node != numa_node) {
- struct mcs_spinlock *nnext = READ_ONCE(next->next);
+ if (next_numa_node != CNA_PRIORITY_NODE) {
+ struct mcs_spinlock *nnext = READ_ONCE(next->next);
- if (nnext) {
- cna_splice_next(node, next, nnext);
- next = nnext;
+ if (nnext) {
+ cna_splice_next(node, next, nnext);
+ next = nnext;
+ }
}
/*
* Inherit NUMA node id of primary queue, to maintain the
@@ -287,6 +294,13 @@ static __always_inline u32 cna_wait_head_or_lock(struct qspinlock *lock,
struct cna_node *cn = (struct cna_node *)node;
if (!cn->start_time || !intra_node_threshold_reached(cn)) {
+ /*
+ * We are at the head of the wait queue, no need to use
+ * the fake NUMA node ID.
+ */
+ if (cn->numa_node == CNA_PRIORITY_NODE)
+ cn->numa_node = cn->real_numa_node;
+
/*
* Try and put the time otherwise spent spin waiting on
* _Q_LOCKED_PENDING_MASK to use by sorting our lists.
--
2.24.3 (Apple Git-128)
next prev parent reply other threads:[~2021-04-01 18:55 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 15:31 [PATCH v14 0/6] Add NUMA-awareness to qspinlock Alex Kogan
2021-04-01 15:31 ` [PATCH v14 1/6] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2021-04-01 15:31 ` [PATCH v14 2/6] locking/qspinlock: Refactor the qspinlock slow path Alex Kogan
2021-04-01 15:31 ` [PATCH v14 3/6] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2021-04-13 11:30 ` Peter Zijlstra
2021-04-14 2:29 ` [External] : " Alex Kogan
2021-04-01 15:31 ` [PATCH v14 4/6] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2021-04-13 6:03 ` Andi Kleen
2021-04-13 6:12 ` Andi Kleen
2021-04-13 21:01 ` [External] : " Alex Kogan
2021-04-13 21:22 ` Andi Kleen
2021-04-14 2:30 ` Alex Kogan
2021-04-14 16:41 ` Waiman Long
2021-04-14 17:26 ` Andi Kleen
2021-04-14 17:31 ` Waiman Long
2021-04-13 12:03 ` Peter Zijlstra
2021-04-16 2:52 ` [External] : " Alex Kogan
2021-04-01 15:31 ` Alex Kogan [this message]
2021-04-01 15:31 ` [PATCH v14 6/6] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2021-04-14 7:47 ` Andreas Herrmann
2021-04-14 18:18 ` [External] : " Alex Kogan
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