Latency is in the eye of the beholder. In the case where a client stops
and waits for the gpu, give that request chain a small priority boost
(not so that it overtakes higher priority clients, to preserve the
external ordering) so that ideally the wait completes earlier.
v2: Tvrtko recommends to keep the boost-from-user-stall as small as
possible and to allow new client flows to be preferred for interactivity
over stalls.
Testcase: igt/gem_sync/switch-default
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@xxxxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 5 +++-
drivers/gpu/drm/i915/i915_request.c | 2 ++
drivers/gpu/drm/i915/i915_request.h | 5 ++--
drivers/gpu/drm/i915/i915_scheduler.c | 34 ++++++++++++++++++++++-----
drivers/gpu/drm/i915/i915_scheduler.h | 7 ++++--
5 files changed, 42 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index db9688d14912..63fb886d0aff 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1748,6 +1748,7 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
*/
err = i915_gem_object_wait(obj,
I915_WAIT_INTERRUPTIBLE |
+ I915_WAIT_PRIORITY |
(write_domain ? I915_WAIT_ALL : 0),
MAX_SCHEDULE_TIMEOUT,
to_rps_client(file));
@@ -3751,7 +3752,9 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
start = ktime_get();
ret = i915_gem_object_wait(obj,
- I915_WAIT_INTERRUPTIBLE | I915_WAIT_ALL,
+ I915_WAIT_INTERRUPTIBLE |
+ I915_WAIT_PRIORITY |
+ I915_WAIT_ALL,
to_wait_timeout(args->timeout_ns),
to_rps_client(file));
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index d73ad490a261..abd4dacbab8e 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1237,6 +1237,8 @@ long i915_request_wait(struct i915_request *rq,
add_wait_queue(errq, &reset);
intel_wait_init(&wait);
+ if (flags & I915_WAIT_PRIORITY)
+ i915_schedule_bump_priority(rq, I915_PRIORITY_WAIT);
restart:
do {
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 5f7361e0fca6..90e9d170a0cd 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -277,8 +277,9 @@ long i915_request_wait(struct i915_request *rq,
__attribute__((nonnull(1)));
#define I915_WAIT_INTERRUPTIBLE BIT(0)
#define I915_WAIT_LOCKED BIT(1) /* struct_mutex held, handle GPU reset */
-#define I915_WAIT_ALL BIT(2) /* used by i915_gem_object_wait() */
-#define I915_WAIT_FOR_IDLE_BOOST BIT(3)
+#define I915_WAIT_PRIORITY BIT(2) /* small priority bump for the request */
+#define I915_WAIT_ALL BIT(3) /* used by i915_gem_object_wait() */
+#define I915_WAIT_FOR_IDLE_BOOST BIT(4)
static inline bool intel_engine_has_started(struct intel_engine_cs *engine,
u32 seqno);
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 7bfc82f089e1..fcd98bf93f31 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -239,7 +239,8 @@ sched_lock_engine(struct i915_sched_node *node, struct intel_engine_cs *locked)
return engine;
}
-void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
+static void __i915_schedule(struct i915_request *rq,
+ const struct i915_sched_attr *attr)
{
struct list_head *uninitialized_var(pl);
struct intel_engine_cs *engine, *last;
@@ -248,6 +249,8 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
const int prio = attr->priority;
LIST_HEAD(dfs);
+ /* Needed in order to use the temporary link inside i915_dependency */
+ lockdep_assert_held(&schedule_lock);
GEM_BUG_ON(prio == I915_PRIORITY_INVALID);
if (i915_request_completed(rq))
@@ -256,9 +259,6 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
if (prio <= READ_ONCE(rq->sched.attr.priority))
return;
- /* Needed in order to use the temporary link inside i915_dependency */
- spin_lock(&schedule_lock);
-
stack.signaler = &rq->sched;
list_add(&stack.dfs_link, &dfs);
@@ -312,7 +312,7 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
rq->sched.attr = *attr;
if (stack.dfs_link.next == stack.dfs_link.prev)
- goto out_unlock;
+ return;
__list_del_entry(&stack.dfs_link);
}
@@ -371,7 +371,29 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
}
spin_unlock_irq(&engine->timeline.lock);
+}
-out_unlock:
+void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
+{
+ spin_lock(&schedule_lock);
+ __i915_schedule(rq, attr);
spin_unlock(&schedule_lock);
}
+
+void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump)
+{
+ struct i915_sched_attr attr;
+
+ GEM_BUG_ON(bump & ~I915_PRIORITY_MASK);
+
+ if (READ_ONCE(rq->sched.attr.priority) == I915_PRIORITY_INVALID)
+ return;
+
+ spin_lock_bh(&schedule_lock);
+
+ attr = rq->sched.attr;
+ attr.priority |= bump;
+ __i915_schedule(rq, &attr);
+
+ spin_unlock_bh(&schedule_lock);
+}
diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
index 68d84a45ad7f..dbe9cb7ecd82 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.h
+++ b/drivers/gpu/drm/i915/i915_scheduler.h
@@ -24,13 +24,14 @@ enum {
I915_PRIORITY_INVALID = INT_MIN
};
-#define I915_USER_PRIORITY_SHIFT 1
+#define I915_USER_PRIORITY_SHIFT 2
#define I915_USER_PRIORITY(x) ((x) << I915_USER_PRIORITY_SHIFT)
#define I915_PRIORITY_COUNT BIT(I915_USER_PRIORITY_SHIFT)
#define I915_PRIORITY_MASK (I915_PRIORITY_COUNT - 1)
-#define I915_PRIORITY_NEWCLIENT ((u8)BIT(0))
+#define I915_PRIORITY_WAIT ((u8)BIT(0))
+#define I915_PRIORITY_NEWCLIENT ((u8)BIT(1))
struct i915_sched_attr {
/**
@@ -99,6 +100,8 @@ void i915_sched_node_fini(struct drm_i915_private *i915,
void i915_schedule(struct i915_request *request,
const struct i915_sched_attr *attr);
+void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump);
+
struct list_head *
i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio);
--
2.19.0
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