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path: root/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
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Diffstat (limited to 'drivers/gpu/drm/i915/gt/intel_breadcrumbs.c')
-rw-r--r--drivers/gpu/drm/i915/gt/intel_breadcrumbs.c143
1 files changed, 92 insertions, 51 deletions
diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index d8b206e53660..cf6e05ea4d8f 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -30,18 +30,21 @@
#include "i915_trace.h"
#include "intel_breadcrumbs.h"
#include "intel_context.h"
+#include "intel_engine_pm.h"
#include "intel_gt_pm.h"
#include "intel_gt_requests.h"
-static void irq_enable(struct intel_engine_cs *engine)
+static bool irq_enable(struct intel_engine_cs *engine)
{
if (!engine->irq_enable)
- return;
+ return false;
/* Caller disables interrupts */
spin_lock(&engine->gt->irq_lock);
engine->irq_enable(engine);
spin_unlock(&engine->gt->irq_lock);
+
+ return true;
}
static void irq_disable(struct intel_engine_cs *engine)
@@ -57,12 +60,11 @@ static void irq_disable(struct intel_engine_cs *engine)
static void __intel_breadcrumbs_arm_irq(struct intel_breadcrumbs *b)
{
- lockdep_assert_held(&b->irq_lock);
-
- if (!b->irq_engine || b->irq_armed)
- return;
-
- if (!intel_gt_pm_get_if_awake(b->irq_engine->gt))
+ /*
+ * Since we are waiting on a request, the GPU should be busy
+ * and should have its own rpm reference.
+ */
+ if (GEM_WARN_ON(!intel_gt_pm_get_if_awake(b->irq_engine->gt)))
return;
/*
@@ -73,25 +75,24 @@ static void __intel_breadcrumbs_arm_irq(struct intel_breadcrumbs *b)
*/
WRITE_ONCE(b->irq_armed, true);
- /*
- * Since we are waiting on a request, the GPU should be busy
- * and should have its own rpm reference. This is tracked
- * by i915->gt.awake, we can forgo holding our own wakref
- * for the interrupt as before i915->gt.awake is released (when
- * the driver is idle) we disarm the breadcrumbs.
- */
-
- if (!b->irq_enabled++)
- irq_enable(b->irq_engine);
+ /* Requests may have completed before we could enable the interrupt. */
+ if (!b->irq_enabled++ && irq_enable(b->irq_engine))
+ irq_work_queue(&b->irq_work);
}
-static void __intel_breadcrumbs_disarm_irq(struct intel_breadcrumbs *b)
+static void intel_breadcrumbs_arm_irq(struct intel_breadcrumbs *b)
{
- lockdep_assert_held(&b->irq_lock);
-
- if (!b->irq_engine || !b->irq_armed)
+ if (!b->irq_engine)
return;
+ spin_lock(&b->irq_lock);
+ if (!b->irq_armed)
+ __intel_breadcrumbs_arm_irq(b);
+ spin_unlock(&b->irq_lock);
+}
+
+static void __intel_breadcrumbs_disarm_irq(struct intel_breadcrumbs *b)
+{
GEM_BUG_ON(!b->irq_enabled);
if (!--b->irq_enabled)
irq_disable(b->irq_engine);
@@ -105,8 +106,6 @@ static void add_signaling_context(struct intel_breadcrumbs *b,
{
intel_context_get(ce);
list_add_tail(&ce->signal_link, &b->signalers);
- if (list_is_first(&ce->signal_link, &b->signalers))
- __intel_breadcrumbs_arm_irq(b);
}
static void remove_signaling_context(struct intel_breadcrumbs *b,
@@ -174,34 +173,65 @@ static void add_retire(struct intel_breadcrumbs *b, struct intel_timeline *tl)
intel_engine_add_retire(b->irq_engine, tl);
}
-static bool __signal_request(struct i915_request *rq, struct list_head *signals)
+static bool __signal_request(struct i915_request *rq)
{
- clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
-
if (!__dma_fence_signal(&rq->fence)) {
i915_request_put(rq);
return false;
}
- list_add_tail(&rq->signal_link, signals);
return true;
}
+static struct llist_node *
+slist_add(struct llist_node *node, struct llist_node *head)
+{
+ node->next = head;
+ return node;
+}
+
static void signal_irq_work(struct irq_work *work)
{
struct intel_breadcrumbs *b = container_of(work, typeof(*b), irq_work);
const ktime_t timestamp = ktime_get();
+ struct llist_node *signal, *sn;
struct intel_context *ce, *cn;
struct list_head *pos, *next;
- LIST_HEAD(signal);
+
+ signal = NULL;
+ if (unlikely(!llist_empty(&b->signaled_requests)))
+ signal = llist_del_all(&b->signaled_requests);
spin_lock(&b->irq_lock);
- if (list_empty(&b->signalers))
+ /*
+ * Keep the irq armed until the interrupt after all listeners are gone.
+ *
+ * Enabling/disabling the interrupt is rather costly, roughly a couple
+ * of hundred microseconds. If we are proactive and enable/disable
+ * the interrupt around every request that wants a breadcrumb, we
+ * quickly drown in the extra orders of magnitude of latency imposed
+ * on request submission.
+ *
+ * So we try to be lazy, and keep the interrupts enabled until no
+ * more listeners appear within a breadcrumb interrupt interval (that
+ * is until a request completes that no one cares about). The
+ * observation is that listeners come in batches, and will often
+ * listen to a bunch of requests in succession. Though note on icl+,
+ * interrupts are always enabled due to concerns with rc6 being
+ * dysfunctional with per-engine interrupt masking.
+ *
+ * We also try to avoid raising too many interrupts, as they may
+ * be generated by userspace batches and it is unfortunately rather
+ * too easy to drown the CPU under a flood of GPU interrupts. Thus
+ * whenever no one appears to be listening, we turn off the interrupts.
+ * Fewer interrupts should conserve power -- at the very least, fewer
+ * interrupt draw less ire from other users of the system and tools
+ * like powertop.
+ */
+ if (!signal && b->irq_armed && list_empty(&b->signalers))
__intel_breadcrumbs_disarm_irq(b);
- list_splice_init(&b->signaled_requests, &signal);
-
list_for_each_entry_safe(ce, cn, &b->signalers, signal_link) {
GEM_BUG_ON(list_empty(&ce->signals));
@@ -218,7 +248,10 @@ static void signal_irq_work(struct irq_work *work)
* spinlock as the callback chain may end up adding
* more signalers to the same context or engine.
*/
- __signal_request(rq, &signal);
+ clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
+ if (__signal_request(rq))
+ /* We own signal_node now, xfer to local list */
+ signal = slist_add(&rq->signal_node, signal);
}
/*
@@ -238,9 +271,9 @@ static void signal_irq_work(struct irq_work *work)
spin_unlock(&b->irq_lock);
- list_for_each_safe(pos, next, &signal) {
+ llist_for_each_safe(signal, sn, signal) {
struct i915_request *rq =
- list_entry(pos, typeof(*rq), signal_link);
+ llist_entry(signal, typeof(*rq), signal_node);
struct list_head cb_list;
spin_lock(&rq->lock);
@@ -251,6 +284,9 @@ static void signal_irq_work(struct irq_work *work)
i915_request_put(rq);
}
+
+ if (!READ_ONCE(b->irq_armed) && !list_empty(&b->signalers))
+ intel_breadcrumbs_arm_irq(b);
}
struct intel_breadcrumbs *
@@ -264,7 +300,7 @@ intel_breadcrumbs_create(struct intel_engine_cs *irq_engine)
spin_lock_init(&b->irq_lock);
INIT_LIST_HEAD(&b->signalers);
- INIT_LIST_HEAD(&b->signaled_requests);
+ init_llist_head(&b->signaled_requests);
init_irq_work(&b->irq_work, signal_irq_work);
@@ -292,21 +328,22 @@ void intel_breadcrumbs_reset(struct intel_breadcrumbs *b)
void intel_breadcrumbs_park(struct intel_breadcrumbs *b)
{
- unsigned long flags;
-
- if (!READ_ONCE(b->irq_armed))
- return;
-
- spin_lock_irqsave(&b->irq_lock, flags);
- __intel_breadcrumbs_disarm_irq(b);
- spin_unlock_irqrestore(&b->irq_lock, flags);
-
- if (!list_empty(&b->signalers))
- irq_work_queue(&b->irq_work);
+ /* Kick the work once more to drain the signalers */
+ irq_work_sync(&b->irq_work);
+ while (unlikely(READ_ONCE(b->irq_armed))) {
+ local_irq_disable();
+ signal_irq_work(&b->irq_work);
+ local_irq_enable();
+ cond_resched();
+ }
+ GEM_BUG_ON(!list_empty(&b->signalers));
}
void intel_breadcrumbs_free(struct intel_breadcrumbs *b)
{
+ irq_work_sync(&b->irq_work);
+ GEM_BUG_ON(!list_empty(&b->signalers));
+ GEM_BUG_ON(b->irq_armed);
kfree(b);
}
@@ -327,7 +364,8 @@ static void insert_breadcrumb(struct i915_request *rq,
* its signal completion.
*/
if (__request_completed(rq)) {
- if (__signal_request(rq, &b->signaled_requests))
+ if (__signal_request(rq) &&
+ llist_add(&rq->signal_node, &b->signaled_requests))
irq_work_queue(&b->irq_work);
return;
}
@@ -362,9 +400,12 @@ static void insert_breadcrumb(struct i915_request *rq,
GEM_BUG_ON(!check_signal_order(ce, rq));
set_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags);
- /* Check after attaching to irq, interrupt may have already fired. */
- if (__request_completed(rq))
- irq_work_queue(&b->irq_work);
+ /*
+ * Defer enabling the interrupt to after HW submission and recheck
+ * the request as it may have completed and raised the interrupt as
+ * we were attaching it into the lists.
+ */
+ irq_work_queue(&b->irq_work);
}
bool i915_request_enable_breadcrumb(struct i915_request *rq)