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
Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
alex.kogan@oracle.com, dave.dice@oracle.com,
rahul.x.yadav@oracle.com
Subject: [PATCH v2 2/5] locking/qspinlock: Refactor the qspinlock slow path
Date: Fri, 29 Mar 2019 11:20:03 -0400 [thread overview]
Message-ID: <20190329152006.110370-3-alex.kogan@oracle.com> (raw)
In-Reply-To: <20190329152006.110370-1-alex.kogan@oracle.com>
Move some of the code manipulating MCS nodes into separate functions.
This would allow easier integration of alternative ways to manipulate
those nodes.
Signed-off-by: Alex Kogan <alex.kogan@oracle.com>
Reviewed-by: Steve Sistare <steven.sistare@oracle.com>
---
kernel/locking/qspinlock.c | 48 +++++++++++++++++++++++++++++++++++++++-------
1 file changed, 41 insertions(+), 7 deletions(-)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 5941ce3527ce..074f65b9bedc 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -297,6 +297,43 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock,
#define queued_spin_lock_slowpath native_queued_spin_lock_slowpath
#endif
+static __always_inline int get_node_index(struct mcs_spinlock *node)
+{
+ return node->count++;
+}
+
+static __always_inline void release_mcs_node(struct mcs_spinlock *node)
+{
+ __this_cpu_dec(node->count);
+}
+
+/*
+ * set_locked_empty_mcs - Try to set the spinlock value to _Q_LOCKED_VAL,
+ * and by doing that unlock the MCS lock when its waiting queue is empty
+ * @lock: Pointer to queued spinlock structure
+ * @val: Current value of the lock
+ * @node: Pointer to the MCS node of the lock holder
+ *
+ * *,*,* -> 0,0,1
+ */
+static __always_inline bool set_locked_empty_mcs(struct qspinlock *lock,
+ u32 val,
+ struct mcs_spinlock *node)
+{
+ return atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL);
+}
+
+/*
+ * pass_mcs_lock - pass the MCS lock to the next waiter
+ * @node: Pointer to the MCS node of the lock holder
+ * @next: Pointer to the MCS node of the first waiter in the MCS queue
+ */
+static __always_inline void pass_mcs_lock(struct mcs_spinlock *node,
+ struct mcs_spinlock *next)
+{
+ arch_mcs_spin_unlock_contended(&next->locked, 1);
+}
+
#endif /* _GEN_PV_LOCK_SLOWPATH */
/**
@@ -406,7 +443,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
qstat_inc(qstat_lock_slowpath, true);
pv_queue:
node = this_cpu_ptr(&qnodes[0].mcs);
- idx = node->count++;
+ idx = get_node_index(node);
tail = encode_tail(smp_processor_id(), idx);
/*
@@ -541,7 +578,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
* PENDING will make the uncontended transition fail.
*/
if ((val & _Q_TAIL_MASK) == tail) {
- if (atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL))
+ if (set_locked_empty_mcs(lock, val, node))
goto release; /* No contention */
}
@@ -558,14 +595,11 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
if (!next)
next = smp_cond_load_relaxed(&node->next, (VAL));
- arch_mcs_spin_unlock_contended(&next->locked, 1);
+ pass_mcs_lock(node, next);
pv_kick_node(lock, next);
release:
- /*
- * release the node
- */
- __this_cpu_dec(qnodes[0].mcs.count);
+ release_mcs_node(&qnodes[0].mcs);
}
EXPORT_SYMBOL(queued_spin_lock_slowpath);
--
2.11.0 (Apple Git-81)
next prev parent reply other threads:[~2019-03-29 15:21 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-29 15:20 [PATCH v2 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2019-03-29 15:20 ` [PATCH v2 1/5] locking/qspinlock: Make arch_mcs_spin_unlock_contended more generic Alex Kogan
2019-03-29 15:20 ` Alex Kogan [this message]
2019-03-29 15:20 ` [PATCH v2 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2019-04-01 9:06 ` Peter Zijlstra
2019-04-01 9:33 ` Peter Zijlstra
2019-04-03 15:53 ` Alex Kogan
2019-04-03 16:10 ` Peter Zijlstra
2019-04-01 9:21 ` Peter Zijlstra
2019-04-01 14:36 ` Waiman Long
2019-04-02 9:43 ` Peter Zijlstra
2019-04-03 15:39 ` Alex Kogan
2019-04-03 15:48 ` Waiman Long
2019-04-03 16:01 ` Peter Zijlstra
2019-04-04 5:05 ` Juergen Gross
2019-04-04 9:38 ` Peter Zijlstra
2019-04-04 18:03 ` Waiman Long
2019-06-04 23:21 ` Alex Kogan
2019-06-05 20:40 ` Peter Zijlstra
2019-06-06 15:21 ` Alex Kogan
2019-06-06 15:32 ` Waiman Long
2019-06-06 15:42 ` Waiman Long
2019-04-03 16:33 ` Waiman Long
2019-04-03 17:16 ` Peter Zijlstra
2019-04-03 17:40 ` Waiman Long
2019-04-04 2:02 ` Hanjun Guo
2019-04-04 3:14 ` Alex Kogan
2019-06-11 4:22 ` liwei (GF)
2019-06-12 4:38 ` Alex Kogan
2019-06-12 15:05 ` Waiman Long
2019-03-29 15:20 ` [PATCH v2 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2019-04-02 10:37 ` Peter Zijlstra
2019-04-03 17:06 ` Alex Kogan
2019-03-29 15:20 ` [PATCH v2 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2019-04-01 9:09 ` [PATCH v2 0/5] Add NUMA-awareness to qspinlock Peter Zijlstra
2019-04-03 17:13 ` Alex Kogan
2019-07-03 11:58 ` Jan Glauber
2019-07-12 8:12 ` Hanjun Guo
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