Re: [PATCH 29/32] drm/i915: Apply an execution_mask to the virtual_engine

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 17/04/2019 08:56, Chris Wilson wrote:
> Allow the user to direct which physical engines of the virtual engine
> they wish to execute one, as sometimes it is necessary to override the
> load balancing algorithm.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/gt/intel_lrc.c    |  58 +++++++++++
>   drivers/gpu/drm/i915/gt/selftest_lrc.c | 131 +++++++++++++++++++++++++
>   drivers/gpu/drm/i915/i915_request.c    |   1 +
>   drivers/gpu/drm/i915/i915_request.h    |   3 +
>   4 files changed, 193 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index d6efd6aa67cb..560a18bb4cbb 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -552,6 +552,18 @@ execlists_context_schedule_out(struct i915_request *rq, unsigned long status)
>   	intel_engine_context_out(rq->engine);
>   	execlists_context_status_change(rq, status);
>   	trace_i915_request_out(rq);
> +
> +	/*
> +	 * If this is part of a virtual engine, its next request may have
> +	 * been blocked waiting for access to the active context. We have
> +	 * to kick all the siblings again in case we need to switch (e.g.
> +	 * the next request is not runnable on this engine). Hopefully,
> +	 * we will already have submitted the next request before the
> +	 * tasklet runs and do not need to rebuild each virtual tree
> +	 * and kick everyone again.
> +	 */
> +	if (rq->engine != rq->hw_context->engine)
> +		tasklet_schedule(&rq->hw_context->engine->execlists.tasklet);

Is this needed only for non-default execution_mask? If so it would be 
good to limit it to avoid tasklet storm with plain veng.

>   }
>   
>   static u64 execlists_update_context(struct i915_request *rq)
> @@ -779,6 +791,9 @@ static bool virtual_matches(const struct virtual_engine *ve,
>   {
>   	const struct intel_engine_cs *active;
>   
> +	if (!(rq->execution_mask & engine->mask)) /* We peeked too soon! */
> +		return false;
> +
>   	/*
>   	 * We track when the HW has completed saving the context image
>   	 * (i.e. when we have seen the final CS event switching out of
> @@ -3139,12 +3154,44 @@ static const struct intel_context_ops virtual_context_ops = {
>   	.destroy = virtual_context_destroy,
>   };
>   
> +static intel_engine_mask_t virtual_submission_mask(struct virtual_engine *ve)
> +{
> +	struct i915_request *rq;
> +	intel_engine_mask_t mask;

intel_engine_mask_t throughout is the wrong type for this, even if we 
disallowed duplicate siblings, and even more so if we don't.

Either way it seems like the 64 sibling limit needs to be back. Or maybe 
only in the bonding case?

> +
> +	rq = READ_ONCE(ve->request);
> +	if (!rq)
> +		return 0;
> +
> +	/* The rq is ready for submission; rq->execution_mask is now stable. */
> +	mask = rq->execution_mask;
> +	if (unlikely(!mask)) {
> +		/* Invalid selection, submit to a random engine in error */
> +		i915_request_skip(rq, -ENODEV);

When can this happen? It looks like if it can happen we should reject it 
earlier. Or if it can't then just assert.

> +		mask = ve->siblings[0]->mask;
> +	}
> +
> +	GEM_TRACE("%s: rq=%llx:%lld, mask=%x, prio=%d\n",
> +		  ve->base.name,
> +		  rq->fence.context, rq->fence.seqno,
> +		  mask, ve->base.execlists.queue_priority_hint);
> +
> +	return mask;
> +}
> +
>   static void virtual_submission_tasklet(unsigned long data)
>   {
>   	struct virtual_engine * const ve = (struct virtual_engine *)data;
>   	const int prio = ve->base.execlists.queue_priority_hint;
> +	intel_engine_mask_t mask;
>   	unsigned int n;
>   
> +	rcu_read_lock();
> +	mask = virtual_submission_mask(ve);
> +	rcu_read_unlock();

What is the RCU for?

> +	if (unlikely(!mask))
> +		return;
> +
>   	local_irq_disable();
>   	for (n = 0; READ_ONCE(ve->request) && n < ve->num_siblings; n++) {
>   		struct intel_engine_cs *sibling = ve->siblings[n];
> @@ -3152,6 +3199,17 @@ static void virtual_submission_tasklet(unsigned long data)
>   		struct rb_node **parent, *rb;
>   		bool first;
>   
> +		if (unlikely(!(mask & sibling->mask))) {
> +			if (!RB_EMPTY_NODE(&node->rb)) {
> +				spin_lock(&sibling->timeline.lock);
> +				rb_erase_cached(&node->rb,
> +						&sibling->execlists.virtual);
> +				RB_CLEAR_NODE(&node->rb);
> +				spin_unlock(&sibling->timeline.lock);
> +			}
> +			continue;
> +		}
> +
>   		spin_lock(&sibling->timeline.lock);
>   
>   		if (!RB_EMPTY_NODE(&node->rb)) {
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index f34aa9e042a3..209e51ef13e6 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -1480,6 +1480,136 @@ static int live_virtual_engine(void *arg)
>   	return err;
>   }
>   
> +static int mask_virtual_engine(struct drm_i915_private *i915,
> +			       struct intel_engine_cs **siblings,
> +			       unsigned int nsibling)
> +{
> +	struct i915_request *request[MAX_ENGINE_INSTANCE + 1];
> +	struct i915_gem_context *ctx;
> +	struct intel_context *ve;
> +	struct igt_live_test t;
> +	unsigned int n;
> +	int err;
> +
> +	/*
> +	 * Check that by setting the execution mask on a request, we can
> +	 * restrict it to our desired engine within the virtual engine.
> +	 */
> +
> +	ctx = kernel_context(i915);
> +	if (!ctx)
> +		return -ENOMEM;
> +
> +	ve = intel_execlists_create_virtual(ctx, siblings, nsibling);
> +	if (IS_ERR(ve)) {
> +		err = PTR_ERR(ve);
> +		goto out_close;
> +	}
> +
> +	err = intel_context_pin(ve);
> +	if (err)
> +		goto out_put;
> +
> +	err = igt_live_test_begin(&t, i915, __func__, ve->engine->name);
> +	if (err)
> +		goto out_unpin;
> +
> +	for (n = 0; n < nsibling; n++) {
> +		request[n] = i915_request_create(ve);
> +		if (IS_ERR(request)) {
> +			err = PTR_ERR(request);
> +			nsibling = n;
> +			goto out;
> +		}
> +
> +		/* Reverse order as it's more likely to be unnatural */
> +		request[n]->execution_mask = siblings[nsibling - n - 1]->mask;
> +
> +		i915_request_get(request[n]);
> +		i915_request_add(request[n]);
> +	}
> +
> +	for (n = 0; n < nsibling; n++) {
> +		if (i915_request_wait(request[n], I915_WAIT_LOCKED, HZ / 10) < 0) {
> +			pr_err("%s(%s): wait for %llx:%lld timed out\n",
> +			       __func__, ve->engine->name,
> +			       request[n]->fence.context,
> +			       request[n]->fence.seqno);
> +
> +			GEM_TRACE("%s(%s) failed at request %llx:%lld\n",
> +				  __func__, ve->engine->name,
> +				  request[n]->fence.context,
> +				  request[n]->fence.seqno);
> +			GEM_TRACE_DUMP();
> +			i915_gem_set_wedged(i915);
> +			err = -EIO;
> +			goto out;
> +		}
> +
> +		if (request[n]->engine != siblings[nsibling - n - 1]) {
> +			pr_err("Executed on wrong sibling '%s', expected '%s'\n",
> +			       request[n]->engine->name,
> +			       siblings[nsibling - n - 1]->name);
> +			err = -EINVAL;
> +			goto out;
> +		}
> +	}
> +
> +	err = igt_live_test_end(&t);
> +	if (err)
> +		goto out;
> +
> +out:
> +	if (igt_flush_test(i915, I915_WAIT_LOCKED))
> +		err = -EIO;
> +
> +	for (n = 0; n < nsibling; n++)
> +		i915_request_put(request[n]);
> +
> +out_unpin:
> +	intel_context_unpin(ve);
> +out_put:
> +	intel_context_put(ve);
> +out_close:
> +	kernel_context_close(ctx);
> +	return err;
> +}
> +
> +static int live_virtual_mask(void *arg)
> +{
> +	struct drm_i915_private *i915 = arg;
> +	struct intel_engine_cs *siblings[MAX_ENGINE_INSTANCE + 1];
> +	unsigned int class, inst;
> +	int err = 0;
> +
> +	if (USES_GUC_SUBMISSION(i915))
> +		return 0;
> +
> +	mutex_lock(&i915->drm.struct_mutex);
> +
> +	for (class = 0; class <= MAX_ENGINE_CLASS; class++) {
> +		unsigned int nsibling;
> +
> +		nsibling = 0;
> +		for (inst = 0; inst <= MAX_ENGINE_INSTANCE; inst++) {
> +			if (!i915->engine_class[class][inst])
> +				break;
> +
> +			siblings[nsibling++] = i915->engine_class[class][inst];
> +		}
> +		if (nsibling < 2)
> +			continue;
> +
> +		err = mask_virtual_engine(i915, siblings, nsibling);
> +		if (err)
> +			goto out_unlock;
> +	}
> +
> +out_unlock:
> +	mutex_unlock(&i915->drm.struct_mutex);
> +	return err;
> +}
> +
>   int intel_execlists_live_selftests(struct drm_i915_private *i915)
>   {
>   	static const struct i915_subtest tests[] = {
> @@ -1493,6 +1623,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
>   		SUBTEST(live_preempt_hang),
>   		SUBTEST(live_preempt_smoke),
>   		SUBTEST(live_virtual_engine),
> +		SUBTEST(live_virtual_mask),
>   	};
>   
>   	if (!HAS_EXECLISTS(i915))
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 46f4fc2a8840..78c07e131521 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -688,6 +688,7 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
>   	rq->batch = NULL;
>   	rq->capture_list = NULL;
>   	rq->waitboost = false;
> +	rq->execution_mask = ALL_ENGINES;
>   
>   	INIT_LIST_HEAD(&rq->active_list);
>   	INIT_LIST_HEAD(&rq->execute_cb);
> diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
> index 8025a89b5999..d7f9b2194568 100644
> --- a/drivers/gpu/drm/i915/i915_request.h
> +++ b/drivers/gpu/drm/i915/i915_request.h
> @@ -28,6 +28,8 @@
>   #include <linux/dma-fence.h>
>   #include <linux/lockdep.h>
>   
> +#include "gt/intel_engine_types.h"
> +
>   #include "i915_gem.h"
>   #include "i915_scheduler.h"
>   #include "i915_selftest.h"
> @@ -156,6 +158,7 @@ struct i915_request {
>   	 */
>   	struct i915_sched_node sched;
>   	struct i915_dependency dep;
> +	intel_engine_mask_t execution_mask;
>   
>   	/*
>   	 * A convenience pointer to the current breadcrumb value stored in
> 

Regards,

Tvrtko
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx