From: Willy Tarreau <w@1wt.eu>
Date: Thu, 16 Jun 2022 13:59:36 +0000 (+0200)
Subject: MINOR: task: replace global_tasks_mask with a check for tree's emptiness
X-Git-Tag: v2.7-dev2~141
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c958c70ec8bca6f816cf93f58e9089b01cc94d33;p=thirdparty%2Fhaproxy.git

MINOR: task: replace global_tasks_mask with a check for tree's emptiness

This bit field used to be a per-thread cache of the result of the last
lookup of the presence of a task for each thread in the shared cache.
Since we now know that each thread has its own shared cache, a test of
emptiness is now sufficient to decide whether or not the shared tree
has a task for the current thread. Let's just remove this mask.
---

diff --git a/include/haproxy/task.h b/include/haproxy/task.h
index 4fb1fe31cf..03ade6fc66 100644
--- a/include/haproxy/task.h
+++ b/include/haproxy/task.h
@@ -89,7 +89,6 @@
 
 
 /* a few exported variables */
-extern volatile unsigned long global_tasks_mask; /* Mask of threads with tasks in the global runqueue */
 extern unsigned int niced_tasks;  /* number of niced tasks in the run queue */
 
 extern struct pool_head *pool_head_task;
@@ -182,8 +181,8 @@ static inline int task_in_wq(struct task *t)
 /* returns true if the current thread has some work to do */
 static inline int thread_has_tasks(void)
 {
-	return ((int)!!(global_tasks_mask & tid_bit) |
-		(int)!eb_is_empty(&th_ctx->rqueue) |
+	return ((int)!eb_is_empty(&th_ctx->rqueue) |
+	        (int)!eb_is_empty(&th_ctx->rqueue_shared) |
 	        (int)!!th_ctx->tl_class_mask |
 		(int)!MT_LIST_ISEMPTY(&th_ctx->shared_tasklet_list));
 }
diff --git a/src/debug.c b/src/debug.c
index 1e9a5ca4d7..a55d087b05 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -168,7 +168,7 @@ void ha_thread_dump(struct buffer *buf, int thr, int calling_tid)
 	              (thr == calling_tid) ? '*' : ' ', stuck ? '>' : ' ', thr + 1,
 		      ha_get_pthread_id(thr),
 		      thread_has_tasks(),
-	              !!(global_tasks_mask & thr_bit),
+	              !eb_is_empty(&ha_thread_ctx[thr].rqueue_shared),
 	              !eb_is_empty(&ha_thread_ctx[thr].timers),
 	              !eb_is_empty(&ha_thread_ctx[thr].rqueue),
 	              !(LIST_ISEMPTY(&ha_thread_ctx[thr].tasklets[TL_URGENT]) &&
diff --git a/src/task.c b/src/task.c
index f0ca126ceb..29505b9bf2 100644
--- a/src/task.c
+++ b/src/task.c
@@ -35,7 +35,6 @@ DECLARE_POOL(pool_head_tasklet, "tasklet", sizeof(struct tasklet));
  */
 DECLARE_POOL(pool_head_notification, "notification", sizeof(struct notification));
 
-volatile unsigned long global_tasks_mask = 0; /* Mask of threads with tasks in the global runqueue */
 unsigned int niced_tasks = 0;      /* number of niced tasks in the run queue */
 
 __decl_aligned_rwlock(wq_lock);   /* RW lock related to the wait queue */
@@ -235,10 +234,6 @@ void __task_wakeup(struct task *t)
 		_HA_ATOMIC_INC(&ha_thread_ctx[thr].rq_total);
 		HA_SPIN_LOCK(TASK_RQ_LOCK, &ha_thread_ctx[thr].rqsh_lock);
 
-		if (t->tid < 0)
-			global_tasks_mask = all_threads_mask;
-		else
-			global_tasks_mask |= 1UL << thr;
 		t->rq.key = _HA_ATOMIC_ADD_FETCH(&ha_thread_ctx[thr].rqueue_ticks, 1);
 		__ha_barrier_store();
 	} else
@@ -562,8 +557,7 @@ unsigned int run_tasks_from_lists(unsigned int budgets[])
 
 			if (unlikely(queue > TL_NORMAL &&
 				     budget_mask & (1 << TL_NORMAL) &&
-				     (!eb_is_empty(&th_ctx->rqueue) ||
-				      (global_tasks_mask & tid_bit)))) {
+				     (!eb_is_empty(&th_ctx->rqueue) || !eb_is_empty(&th_ctx->rqueue_shared)))) {
 				/* a task was woken up by a bulk tasklet or another thread */
 				break;
 			}
@@ -784,7 +778,7 @@ void process_runnable_tasks()
 
 	/* normal tasklets list gets a default weight of ~37% */
 	if ((tt->tl_class_mask & (1 << TL_NORMAL)) ||
-	    !eb_is_empty(&th_ctx->rqueue) || (global_tasks_mask & tid_bit))
+	    !eb_is_empty(&th_ctx->rqueue) || !eb_is_empty(&th_ctx->rqueue_shared))
 		max[TL_NORMAL] = default_weights[TL_NORMAL];
 
 	/* bulk tasklets list gets a default weight of ~13% */
@@ -831,16 +825,14 @@ void process_runnable_tasks()
 	lpicked = gpicked = 0;
 	budget = max[TL_NORMAL] - tt->tasks_in_list;
 	while (lpicked + gpicked < budget) {
-		if ((global_tasks_mask & tid_bit) && !grq) {
+		if (!eb_is_empty(&th_ctx->rqueue_shared) && !grq) {
 #ifdef USE_THREAD
 			HA_SPIN_LOCK(TASK_RQ_LOCK, &th_ctx->rqsh_lock);
 			grq = eb32sc_lookup_ge(&th_ctx->rqueue_shared, _HA_ATOMIC_LOAD(&tt->rqueue_ticks) - TIMER_LOOK_BACK, tid_bit);
 			if (unlikely(!grq)) {
 				grq = eb32sc_first(&th_ctx->rqueue_shared, tid_bit);
-				if (!grq) {
-					global_tasks_mask &= ~tid_bit;
+				if (!grq)
 					HA_SPIN_UNLOCK(TASK_RQ_LOCK, &th_ctx->rqsh_lock);
-				}
 			}
 #endif
 		}
@@ -872,10 +864,8 @@ void process_runnable_tasks()
 
 			if (unlikely(!grq)) {
 				grq = eb32sc_first(&th_ctx->rqueue_shared, tid_bit);
-				if (!grq) {
-					global_tasks_mask &= ~tid_bit;
+				if (!grq)
 					HA_SPIN_UNLOCK(TASK_RQ_LOCK, &th_ctx->rqsh_lock);
-				}
 			}
 			gpicked++;
 		}