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OPTIM: task: limit the impact of memory barriers in taks_remove_from_task_list()

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In this function we end up with successive locked operations then a
store barrier, and in addition the compiler has to emit less efficient
code due to a longer jump. There's no need for absolutely updating the
tasks_run_queue counter before clearing the task's leaf pointer, so
let's swap the two operations and benefit from a single barrier as much
as possible. This code is on the hot path and shows about half a percent
of improvement with 8 threads.
This commit is contained in:
Willy Tarreau 2019-03-07 18:44:12 +01:00
parent bc6218e1b0
commit 1e56c70cc9
1 changed files with 2 additions and 4 deletions
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6
include/proto/task.h
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@ -273,11 +273,9 @@ static inline void task_remove_from_task_list(struct task *t)
{ {
LIST_DEL_INIT(&((struct tasklet *)t)->list); LIST_DEL_INIT(&((struct tasklet *)t)->list);
task_per_thread[tid].task_list_size--; task_per_thread[tid].task_list_size--;
if (!TASK_IS_TASKLET(t))
HA_ATOMIC_STORE(&t->rq.node.leaf_p, NULL); // was 0x1
HA_ATOMIC_SUB(&tasks_run_queue, 1); HA_ATOMIC_SUB(&tasks_run_queue, 1);
if (!TASK_IS_TASKLET(t)) {
t->rq.node.leaf_p = NULL; // was 0x1
__ha_barrier_store();
}
} }
/* /*