From 6b26ab14487d24407e2ddbb5a33147badae41622 Mon Sep 17 00:00:00 2001
From: Alex Hornung <ahornung@gmail.com>
Date: Fri, 2 Oct 2009 13:20:30 +0100
Subject: [PATCH] taskqueue - Improve _start_threads, refactor code

* Change taskqueue_start_threads to take another argument, ncpu, which
  specifies on what cpu the thread(s) should be created.
  If ncpu is <= -1 and count is > 1, then each of the count threads is
  allocated in a round robin fashion to each cpu.

* Switch the per-cpu taskqueues to use the new taskqueue threads API.

Discussed-with: Simon "corecode" Schubert
---
 sys/kern/subr_taskqueue.c | 44 ++++++++++++++++----------------------------
 sys/sys/taskqueue.h       |  3 ++-
 2 files changed, 18 insertions(+), 29 deletions(-)

diff --git a/sys/kern/subr_taskqueue.c b/sys/kern/subr_taskqueue.c
index 9b9abb17c4..e160730f02 100644
--- a/sys/kern/subr_taskqueue.c
+++ b/sys/kern/subr_taskqueue.c
@@ -306,19 +306,20 @@ taskqueue_swi_mp_run(void *arg, void *frame)
 }
 
 int
-taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
+taskqueue_start_threads(struct taskqueue **tqp, int count, int pri, int ncpu,
 			const char *fmt, ...)
 {
 	__va_list ap;
 	struct thread *td;
 	struct taskqueue *tq;
-	int i, error;
+	int i, error, cpu;
 	char ktname[MAXCOMLEN];
 
 	if (count <= 0)
 		return EINVAL;
 
 	tq = *tqp;
+	cpu = ncpu;
 
 	__va_start(ap, fmt);
 	kvsnprintf(ktname, MAXCOMLEN, fmt, ap);
@@ -328,8 +329,16 @@ taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
 	    M_WAITOK | M_ZERO);
 
 	for (i = 0; i < count; i++) {
+		/*
+		 * If no specific cpu was specified and more than one thread
+		 * is to be created, we distribute the threads amongst all
+		 * cpus.
+		 */
+		if ((ncpu <= -1) && (count > 1))
+			cpu = i%ncpus;
+
 		error = lwkt_create(taskqueue_thread_loop, tqp,
-		    &tq->tq_threads[i], NULL, TDF_STOPREQ | TDF_MPSAFE, -1,
+		    &tq->tq_threads[i], NULL, TDF_STOPREQ | TDF_MPSAFE, cpu,
 		    "%s_%d", ktname, i);
 		if (error) {
 			kprintf("%s: kthread_add(%s): error %d", __func__,
@@ -356,7 +365,7 @@ taskqueue_thread_loop(void *arg)
 	TQ_LOCK(tq);
 	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
 		taskqueue_run(tq);
-		TQ_SLEEP(tq, tq, "-");
+		TQ_SLEEP(tq, tq, "tqthr");
 	}
 
 	/* rendezvous with thread that asked us to terminate */
@@ -387,26 +396,6 @@ TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, 0,
 TASKQUEUE_DEFINE(swi_mp, taskqueue_swi_enqueue, 0,
 	 register_swi(SWI_TQ, taskqueue_swi_mp_run, NULL, "swi_mp_taskq", NULL));
 
-static void
-taskqueue_kthread(void *arg)
-{
-	struct taskqueue *queue = taskqueue_thread[mycpuid];
-
-	for (;;) {
-		taskqueue_run(queue);
-		TQ_LOCK(queue);
-		if (STAILQ_EMPTY(&queue->tq_queue))
-			TQ_SLEEP(queue, queue, "tqthr");
-		TQ_UNLOCK(queue);
-	}
-}
-
-static void
-taskqueue_kthread_enqueue(void *context)
-{
-	wakeup(taskqueue_thread[mycpuid]);
-}
-
 struct taskqueue *taskqueue_thread[MAXCPU];
 static struct thread *taskqueue_thread_td[MAXCPU];
 
@@ -420,10 +409,9 @@ taskqueue_init(void)
 
 	for (cpu = 0; cpu < ncpus; cpu++) {
 		taskqueue_thread[cpu] = taskqueue_create("thread", M_INTWAIT,
-		    taskqueue_kthread_enqueue, NULL);
-		lwkt_create(taskqueue_kthread, NULL,
-		    &taskqueue_thread_td[cpu], NULL,
-		    0, cpu, "taskqueue %d", cpu);
+		    taskqueue_thread_enqueue, &taskqueue_thread[cpu]);
+		taskqueue_start_threads(&taskqueue_thread[cpu], 1,
+		    TDPRI_KERN_DAEMON, cpu, "taskq_cpu");
 	}
 }
 
diff --git a/sys/sys/taskqueue.h b/sys/sys/taskqueue.h
index 334e472372..d07d555a70 100644
--- a/sys/sys/taskqueue.h
+++ b/sys/sys/taskqueue.h
@@ -67,7 +67,8 @@ struct taskqueue *taskqueue_create(const char *name, int mflags,
 				    taskqueue_enqueue_fn enqueue,
 				    void *context);
 int	taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
-				const char *name, ...) __printflike(4, 5);
+				int ncpu, const char *name, ...)
+				__printflike(5, 6);
 int	taskqueue_enqueue(struct taskqueue *queue, struct task *task);
 void	taskqueue_drain(struct taskqueue *queue, struct task *task);
 struct taskqueue *taskqueue_find(const char *name);
-- 
2.11.4.GIT