The objpool_push can only happen on local cpu node, so only the local
cpu can touch slot->tail and slot->last, which ensures the correctness
of using cmpxchg without lock prefix (using try_cmpxchg_local instead
of try_cmpxchg_acquire).
Testing with IACA found the lock version of pop/push pair costs 16.46
cycles and local-push version costs 15.63 cycles. Kretprobe throughput
is improved to 1.019 times of the lock version for x86_64 systems.
OS: Debian 10 X86_64, Linux 6.6rc6 with freelist
HW: XEON 8336C x 2, 64 cores/128 threads, DDR4 3200MT/s
1T 2T 4T 8T 16T
lock: 29909085 59865637 119692073 239750369 478005250
local: 30297523 60532376 121147338 242598499 484620355
32T 48T 64T 96T 128T
lock: 957553042 1435814086 1680872925 2043126796 2165424198
local: 968526317 1454991286 1861053557 2059530343 2171732306
Signed-off-by: wuqiang.matt <wuqiang.m...@bytedance.com>
---
lib/objpool.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/objpool.c b/lib/objpool.c
index ce0087f64400..a032701beccb 100644
--- a/lib/objpool.c
+++ b/lib/objpool.c
@@ -166,7 +166,7 @@ objpool_try_add_slot(void *obj, struct objpool_head *pool,
int cpu)
head = READ_ONCE(slot->head);
/* fault caught: something must be wrong */
WARN_ON_ONCE(tail - head > pool->nr_objs);
- } while (!try_cmpxchg_acquire(&slot->tail, &tail, tail + 1));
+ } while (!try_cmpxchg_local(&slot->tail, &tail, tail + 1));
/* now the tail position is reserved for the given obj */
WRITE_ONCE(slot->entries[tail & slot->mask], obj);
--
2.40.1
