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seqlock: Improve seqlock performance.

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This commit improved the seqlock performance on non-SMP and SMP
platforms by 31.7% on average (83Mops -> 106Mops, tested on qemu-intel64/KVM).

Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>
This commit is contained in:
ouyangxiangzhen
2025-09-22 14:31:54 +08:00
committed by Alan C. Assis
parent ef1fb35462
commit a8724387e7
1 changed files with 10 additions and 6 deletions
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include/nuttx/seqlock.h
+10 -6
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@@ -34,7 +34,7 @@
* Pre-processor Definitions * Pre-processor Definitions
****************************************************************************/ ****************************************************************************/
#define SEQLOCK_INITIALIZER {0} #define SEQLOCK_INITIALIZER { 1u, 1u }
/**************************************************************************** /****************************************************************************
* Public Data Types * Public Data Types
@@ -47,6 +47,7 @@
typedef struct seqclock typedef struct seqclock
{ {
atomic_t sequence; atomic_t sequence;
uint32_t next_sequence;
} seqcount_t; } seqcount_t;
#undef EXTERN #undef EXTERN
@@ -78,7 +79,8 @@ extern "C"
static inline_function void seqlock_init(FAR seqcount_t *s) static inline_function void seqlock_init(FAR seqcount_t *s)
{ {
atomic_init(&s->sequence, 0u); atomic_init(&s->sequence, 1u);
s->next_sequence = 1u;
} }
/**************************************************************************** /****************************************************************************
@@ -107,7 +109,7 @@ uint32_t read_seqbegin(FAR const seqcount_t *s)
seq = atomic_read_acquire(&s->sequence); seq = atomic_read_acquire(&s->sequence);
} }
while (seq & 1); while (seq == 0u);
return seq; return seq;
} }
@@ -163,11 +165,11 @@ irqstate_t write_seqlock_irqsave(FAR seqcount_t *s)
{ {
sequence = atomic_read(&s->sequence); sequence = atomic_read(&s->sequence);
if (predict_true(!(sequence & 1))) if (predict_true(sequence != 0u))
{ {
/* Try to acquire the lock ownership. */ /* Try to acquire the lock ownership. */
if (atomic_cmpxchg_acquire(&s->sequence, &sequence, sequence + 1)) if (atomic_cmpxchg_acquire(&s->sequence, &sequence, 0u))
{ {
break; break;
} }
@@ -198,7 +200,9 @@ irqstate_t write_seqlock_irqsave(FAR seqcount_t *s)
static inline_function static inline_function
void write_sequnlock_irqrestore(seqcount_t *s, irqstate_t flags) void write_sequnlock_irqrestore(seqcount_t *s, irqstate_t flags)
{ {
atomic_set_release(&s->sequence, s->sequence + 1); uint32_t next = s->next_sequence + 2;
s->next_sequence = next;
atomic_set_release(&s->sequence, next);
up_irq_restore(flags); up_irq_restore(flags);
} }