Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Now that we are careful to always force-restore contexts upon rewinding
> (where necessary), we can restore our optimisation to skip over
> completed active execlists when dequeuing.
>
> Referenecs: 35f3fd8182ba ("drm/i915/execlists: Workaround switching back to a completed context")
> References: 8ab3a3812aa9 ("drm/i915/gt: Incrementally check for rewinding")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> .../drm/i915/gt/intel_execlists_submission.c | 34 +++++++++----------
> 1 file changed, 16 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index 524c8b54d220..ac1be7a632d3 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -1224,12 +1224,20 @@ static void set_preempt_timeout(struct intel_engine_cs *engine,
> active_preempt_timeout(engine, rq));
> }
>
> +static bool completed(const struct i915_request *rq)
> +{
> + if (i915_request_has_sentinel(rq))
> + return false;
> +
> + return __i915_request_is_complete(rq);
> +}
> +
> static void execlists_dequeue(struct intel_engine_cs *engine)
> {
> struct intel_engine_execlists * const execlists = &engine->execlists;
> struct i915_request **port = execlists->pending;
> struct i915_request ** const last_port = port + execlists->port_mask;
> - struct i915_request *last = *execlists->active;
> + struct i915_request *last, * const *active;
> struct virtual_engine *ve;
> struct rb_node *rb;
> bool submit = false;
> @@ -1266,21 +1274,13 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> * i.e. we will retrigger preemption following the ack in case
> * of trouble.
> *
> - * In theory we can skip over completed contexts that have not
> - * yet been processed by events (as those events are in flight):
> - *
> - * while ((last = *active) && i915_request_completed(last))
> - * active++;
> - *
> - * However, the GPU cannot handle this as it will ultimately
> - * find itself trying to jump back into a context it has just
> - * completed and barf.
> */
> + active = execlists->active;
> + while ((last = *active) && completed(last))
> + active++;
>
> if (last) {
> - if (__i915_request_is_complete(last)) {
> - goto check_secondary;
> - } else if (need_preempt(engine, last)) {
> + if (need_preempt(engine, last)) {
> ENGINE_TRACE(engine,
> "preempting last=%llx:%lld, prio=%d, hint=%d\n",
> last->fence.context,
> @@ -1359,9 +1359,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> * we hopefully coalesce several updates into a single
> * submission.
> */
> -check_secondary:
> - if (!list_is_last(&last->sched.link,
> - &engine->active.requests)) {
> + if (active[1]) {
> /*
> * Even if ELSP[1] is occupied and not worthy
> * of timeslices, our queue might be.
> @@ -1562,7 +1560,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> * of ordered contexts.
> */
> if (submit &&
> - memcmp(execlists->active,
> + memcmp(active,
> execlists->pending,
> (port - execlists->pending) * sizeof(*port))) {
> *port = NULL;
> @@ -1570,7 +1568,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> execlists_schedule_in(*port, port - execlists->pending);
>
> WRITE_ONCE(execlists->yield, -1);
> - set_preempt_timeout(engine, *execlists->active);
> + set_preempt_timeout(engine, *active);
> execlists_submit_ports(engine);
> } else {
> ring_set_paused(engine, 0);
> --
> 2.20.1
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