On Thu, Jun 13, 2019 at 11:27:57PM +0200, Mark Kettenis wrote:
> > Date: Wed, 12 Jun 2019 23:57:27 +0200 (CEST)
> > From: Mark Kettenis <[email protected]>
> >
> > > From: "Sven M. Hallberg" <[email protected]>
> > > Date: Wed, 12 Jun 2019 23:18:24 +0200
> > >
> > > Mark Kettenis on Tue, Jun 11 2019:
> > > > The drm(4) codebase really needs multi-threaded task queues [...]
> > > >
> > > > The diff also starts 4 threads for each workqueue that gets created by
> > > > the drm(4) layer. The number 4 is a bit arbitrary but it is the
> > > > number of threads that Linux creates per CPU for a so-called "unbound"
> > > > workqueue which hopefully is enough to always make progress.
> > > >
> > > > Please test.
> > >
> > > Looks good and appears to work fine with two displays (one internal, one
> > > external). Will test with three at work tomorrow.
> > >
> > >
> > > > - dev_priv->hotplug.poll_init_work.tq = systq;
> > >
> > > Intentional?
> >
> > Yes. It removes a local modification that should no longer be necessary.
> >
> > Unfortunately the diff doesn't work with amdgpu. Some more thinking
> > needed...
>
> So here is a diff that fixes the problem as far as I can tell.
> Jonathan, Sven, can you give this a go?
This revised diff does not introduce any new problems with amdgpu as
far as I can tell. Xorg starts/runs, piglit starts and later gets stuck
in dmafence/scheduler related wait channels (as it did before).
>
> Index: dev/pci/drm/drm_linux.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/pci/drm/drm_linux.c,v
> retrieving revision 1.38
> diff -u -p -r1.38 drm_linux.c
> --- dev/pci/drm/drm_linux.c 9 Jun 2019 12:58:30 -0000 1.38
> +++ dev/pci/drm/drm_linux.c 13 Jun 2019 20:53:23 -0000
> @@ -1399,15 +1399,15 @@ drm_linux_init(void)
> {
> if (system_wq == NULL) {
> system_wq = (struct workqueue_struct *)
> - taskq_create("drmwq", 1, IPL_HIGH, 0);
> + taskq_create("drmwq", 4, IPL_HIGH, 0);
> }
> if (system_unbound_wq == NULL) {
> system_unbound_wq = (struct workqueue_struct *)
> - taskq_create("drmubwq", 1, IPL_HIGH, 0);
> + taskq_create("drmubwq", 4, IPL_HIGH, 0);
> }
> if (system_long_wq == NULL) {
> system_long_wq = (struct workqueue_struct *)
> - taskq_create("drmlwq", 1, IPL_HIGH, 0);
> + taskq_create("drmlwq", 4, IPL_HIGH, 0);
> }
>
> if (taskletq == NULL)
> Index: dev/pci/drm/i915/intel_hotplug.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/pci/drm/i915/intel_hotplug.c,v
> retrieving revision 1.2
> diff -u -p -r1.2 intel_hotplug.c
> --- dev/pci/drm/i915/intel_hotplug.c 14 Apr 2019 10:14:52 -0000 1.2
> +++ dev/pci/drm/i915/intel_hotplug.c 13 Jun 2019 20:53:23 -0000
> @@ -619,7 +619,6 @@ void intel_hpd_init_work(struct drm_i915
> INIT_WORK(&dev_priv->hotplug.hotplug_work, i915_hotplug_work_func);
> INIT_WORK(&dev_priv->hotplug.dig_port_work, i915_digport_work_func);
> INIT_WORK(&dev_priv->hotplug.poll_init_work, i915_hpd_poll_init_work);
> - dev_priv->hotplug.poll_init_work.tq = systq;
> INIT_DELAYED_WORK(&dev_priv->hotplug.reenable_work,
> intel_hpd_irq_storm_reenable_work);
> }
> Index: kern/kern_task.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/kern_task.c,v
> retrieving revision 1.25
> diff -u -p -r1.25 kern_task.c
> --- kern/kern_task.c 28 Apr 2019 04:20:40 -0000 1.25
> +++ kern/kern_task.c 13 Jun 2019 20:53:23 -0000
> @@ -43,6 +43,7 @@ struct taskq {
> TQ_S_DESTROYED
> } tq_state;
> unsigned int tq_running;
> + unsigned int tq_waiting;
> unsigned int tq_nthreads;
> unsigned int tq_flags;
> const char *tq_name;
> @@ -59,6 +60,7 @@ static const char taskq_sys_name[] = "sy
> struct taskq taskq_sys = {
> TQ_S_CREATED,
> 0,
> + 0,
> 1,
> 0,
> taskq_sys_name,
> @@ -77,6 +79,7 @@ static const char taskq_sys_mp_name[] =
> struct taskq taskq_sys_mp = {
> TQ_S_CREATED,
> 0,
> + 0,
> 1,
> TASKQ_MPSAFE,
> taskq_sys_mp_name,
> @@ -122,6 +125,7 @@ taskq_create(const char *name, unsigned
>
> tq->tq_state = TQ_S_CREATED;
> tq->tq_running = 0;
> + tq->tq_waiting = 0;
> tq->tq_nthreads = nthreads;
> tq->tq_name = name;
> tq->tq_flags = flags;
> @@ -223,6 +227,7 @@ taskq_barrier(struct taskq *tq)
>
> WITNESS_CHECKORDER(&tq->tq_lock_object, LOP_NEWORDER, NULL);
>
> + SET(t.t_flags, TASK_BARRIER);
> task_add(tq, &t);
> cond_wait(&c, "tqbar");
> }
> @@ -238,6 +243,7 @@ taskq_del_barrier(struct taskq *tq, stru
> if (task_del(tq, del))
> return;
>
> + SET(t.t_flags, TASK_BARRIER);
> task_add(tq, &t);
> cond_wait(&c, "tqbar");
> }
> @@ -304,13 +310,26 @@ taskq_next_work(struct taskq *tq, struct
> struct task *next;
>
> mtx_enter(&tq->tq_mtx);
> +retry:
> while ((next = TAILQ_FIRST(&tq->tq_worklist)) == NULL) {
> if (tq->tq_state != TQ_S_RUNNING) {
> mtx_leave(&tq->tq_mtx);
> return (0);
> }
>
> + tq->tq_waiting++;
> msleep(tq, &tq->tq_mtx, PWAIT, "bored", 0);
> + tq->tq_waiting--;
> + }
> +
> + if (ISSET(next->t_flags, TASK_BARRIER)) {
> + if (++tq->tq_waiting == tq->tq_nthreads) {
> + tq->tq_waiting--;
> + } else {
> + msleep(tq, &tq->tq_mtx, PWAIT, "tqblk", 0);
> + tq->tq_waiting--;
> + goto retry;
> + }
> }
>
> TAILQ_REMOVE(&tq->tq_worklist, next, t_entry);
> Index: sys/task.h
> ===================================================================
> RCS file: /cvs/src/sys/sys/task.h,v
> retrieving revision 1.15
> diff -u -p -r1.15 task.h
> --- sys/task.h 28 Apr 2019 04:20:40 -0000 1.15
> +++ sys/task.h 13 Jun 2019 20:53:23 -0000
> @@ -31,6 +31,7 @@ struct task {
> };
>
> #define TASK_ONQUEUE 1
> +#define TASK_BARRIER 2
>
> TAILQ_HEAD(task_list, task);
>
>
