Re: [PATCH 2/4] locking/osq_lock: Turn to dynamic switch function from osq_lock/unlock.
From: Waiman Long
Date: Sat Sep 14 2024 - 12:06:28 EST
On 9/14/24 04:53, yongli-oc wrote:
To support numa-aware osq lock, the struct optimistic_spin_queue
is accessed as three members, numa_enable, index, tail16, by union.
The size of the struct is the same as before.
If dynamic numa-ware lock enable, turns to the crossing, x_osq_lock to
check contention level and starts dynamic switch.
Signed-off-by: yongli-oc <yongli-oc@xxxxxxxxxxx>
---
include/linux/osq_lock.h | 33 ++++++++++++++++++++-
kernel/locking/osq_lock.c | 62 +++++++++++++++++++++++++++++++++++++--
2 files changed, 91 insertions(+), 4 deletions(-)
diff --git a/include/linux/osq_lock.h b/include/linux/osq_lock.h
index ea8fb31379e3..37a7bc4ab530 100644
--- a/include/linux/osq_lock.h
+++ b/include/linux/osq_lock.h
@@ -12,14 +12,42 @@ struct optimistic_spin_queue {
* Stores an encoded value of the CPU # of the tail node in the queue.
* If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
*/
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+ union {
+ atomic_t tail;
+ u32 val;
+#ifdef __LITTLE_ENDIAN
+ struct {
+ u16 tail16;
+ u8 index;
+ u8 numa_enable;
+ };
+#else
+ struct {
+ u8 numa_enable;
+ u8 index;
+ u16 tail16;
+ };
+#endif
+ };
+#else
atomic_t tail;
+#endif
};
#define OSQ_UNLOCKED_VAL (0)
/* Init macro and function. */
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+
+#define OSQ_LOCK_UNLOCKED { .tail = ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
+
+#else
+
#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
+#endif
+
static inline void osq_lock_init(struct optimistic_spin_queue *lock)
{
atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
@@ -28,9 +56,12 @@ static inline void osq_lock_init(struct optimistic_spin_queue *lock)
extern bool osq_lock(struct optimistic_spin_queue *lock);
extern void osq_unlock(struct optimistic_spin_queue *lock);
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+extern bool osq_is_locked(struct optimistic_spin_queue *lock);
+#else
static inline bool osq_is_locked(struct optimistic_spin_queue *lock)
{
return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL;
}
-
+#endif
#endif
diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index 75a6f6133866..a7b516939e00 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -2,7 +2,10 @@
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/osq_lock.h>
-
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+#include "numa.h"
+#include "numa_osq.h"
+#endif
These header files are defined in patch 3. You need to rethink about
patch ordering in order not to break bisection.
/*
* An MCS like lock especially tailored for optimistic spinning for sleeping
* lock implementations (mutex, rwsem, etc).
@@ -12,12 +15,34 @@
* spinning.
*/
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+DEFINE_PER_CPU_SHARED_ALIGNED(struct optimistic_spin_node, osq_node);
+/*
+ * We use the value 0 to represent "no CPU", thus the encoded value
+ * will be the CPU number incremented by 1.
+ */
+inline int encode_cpu(int cpu_nr)
+{
+ return cpu_nr + 1;
+}
+
+inline int node_cpu(struct optimistic_spin_node *node)
+{
+ return node->cpu - 1;
+}
+
+inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val)
+{
+ int cpu_nr = encoded_cpu_val - 1;
+
+ return per_cpu_ptr(&osq_node, cpu_nr);
+}
+#else
struct optimistic_spin_node {
struct optimistic_spin_node *next, *prev;
int locked; /* 1 if lock acquired */
int cpu; /* encoded CPU # + 1 value */
};
-
static DEFINE_PER_CPU_SHARED_ALIGNED(struct optimistic_spin_node, osq_node);
/*
@@ -40,6 +65,7 @@ static inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val)
return per_cpu_ptr(&osq_node, cpu_nr);
}
+#endif
/*
* Get a stable @node->next pointer, either for unlock() or unqueue() purposes.
@@ -97,6 +123,14 @@ bool osq_lock(struct optimistic_spin_queue *lock)
int curr = encode_cpu(smp_processor_id());
int old;
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+ if (unlikely(enable_zx_numa_osq_lock > 1)) {
+ node->numa = 1;
+ return x_osq_lock(lock);
+ }
+ node->numa = 0;
+#endif
+
node->locked = 0;
node->next = NULL;
node->cpu = curr;
@@ -108,6 +142,11 @@ bool osq_lock(struct optimistic_spin_queue *lock)
* the lock tail.
*/
old = atomic_xchg(&lock->tail, curr);
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+ if (enable_zx_numa_osq_lock > 0)
+ //enable means all cpu cores are less tan 65534.
+ old = old & 0xffff;
+#endif
if (old == OSQ_UNLOCKED_VAL)
return true;
@@ -212,6 +251,14 @@ void osq_unlock(struct optimistic_spin_queue *lock)
struct optimistic_spin_node *node, *next;
int curr = encode_cpu(smp_processor_id());
+ node = this_cpu_ptr(&osq_node);
+
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+ if (unlikely(enable_zx_numa_osq_lock > 1 &&
+ node->numa == 1))
+ return x_osq_unlock(lock);
+#endif
+
/*
* Fast path for the uncontended case.
*/
@@ -222,7 +269,6 @@ void osq_unlock(struct optimistic_spin_queue *lock)
/*
* Second most likely case.
*/
- node = this_cpu_ptr(&osq_node);
next = xchg(&node->next, NULL);
if (next) {
WRITE_ONCE(next->locked, 1);
@@ -233,3 +279,13 @@ void osq_unlock(struct optimistic_spin_queue *lock)
if (next)
WRITE_ONCE(next->locked, 1);
}
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER_NUMA
+bool osq_is_locked(struct optimistic_spin_queue *lock)
+{
+ if (unlikely(enable_zx_numa_osq_lock > 1))
+ return x_osq_is_locked(lock);
+ return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL;
+}
+#endif
+
+