Re: [PATCH 2/4] locking/osq_lock: Turn to dynamic switch function from osq_lock/unlock.

Waiman Long
2024-09-14T16:06:19Z

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@zhaoxin.com>
> ---
> 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
> +
> +