[master] c6c4915a2 wrk: Track pool statistics separately

[Dridi Boukelmoune]

commit c6c4915a2fbf36afcdc8f745be53315f0d3e791c
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Wed Jun 28 11:07:09 2023 +0200

    wrk: Track pool statistics separately
    
    This makes obvious what is used for statistics purposes and what is used
    to maintain the pool queue. In particular, the pool::nqueued field has
    nothing to do with pool::ndequeued.

diff --git a/bin/varnishd/cache/cache_pool.h b/bin/varnishd/cache/cache_pool.h
index 207e275b1..11bcfbd11 100644
--- a/bin/varnishd/cache/cache_pool.h
+++ b/bin/varnishd/cache/cache_pool.h
@@ -51,10 +51,8 @@ struct pool {
 	struct taskhead			queues[TASK_QUEUE_RESERVE];
 	unsigned			nthr;
 	unsigned			lqueue;
-	uintmax_t			sdropped;
-	uintmax_t			rdropped;
-	uintmax_t			nqueued;
 	uintmax_t			ndequeued;
+	struct VSC_main_pool		stats[1];
 	struct VSC_main_wrk		*a_stat;
 	struct VSC_main_wrk		*b_stat;
 
diff --git a/bin/varnishd/cache/cache_wrk.c b/bin/varnishd/cache/cache_wrk.c
index cc306a1e8..fe4c650b5 100644
--- a/bin/varnishd/cache/cache_wrk.c
+++ b/bin/varnishd/cache/cache_wrk.c
@@ -343,15 +343,20 @@ Pool_Task(struct pool *pp, struct pool_task *task, enum task_prio prio)
 	} else if (!TASK_QUEUE_LIMITED(prio) ||
 	    pp->lqueue + pp->nthr < cache_param->wthread_max +
 	    cache_param->wthread_queue_limit) {
-		pp->nqueued++;
+		pp->stats->sess_queued++;
 		pp->lqueue++;
 		VTAILQ_INSERT_TAIL(&pp->queues[prio], task, list);
 		PTOK(pthread_cond_signal(&pp->herder_cond));
 	} else {
+		/* NB: This is counter-intuitive but when we drop a REQ
+		 * task, it is an HTTP/1 request and we effectively drop
+		 * the whole session. It is otherwise an h2 stream with
+		 * STR priority in which case we are dropping a request.
+		 */
 		if (prio == TASK_QUEUE_REQ)
-			pp->sdropped++;
+			pp->stats->sess_dropped++;
 		else
-			pp->rdropped++;
+			pp->stats->req_dropped++;
 		retval = -1;
 	}
 	Lck_Unlock(&pp->mtx);
@@ -651,10 +656,8 @@ pool_herder(void *priv)
 
 			Lck_Lock(&pp->mtx);
 			/* XXX: unsafe counters */
-			VSC_C_main->sess_queued += pp->nqueued;
-			VSC_C_main->sess_dropped += pp->sdropped;
-			VSC_C_main->req_dropped += pp->rdropped;
-			pp->nqueued = pp->sdropped = pp->rdropped = 0;
+			VSC_main_Summ_pool(VSC_C_main, pp->stats);
+			memset(pp->stats, 0, sizeof pp->stats);
 
 			wrk = NULL;
 			pt = VTAILQ_LAST(&pp->idle_queue, taskhead);