We dropped calling process_csb prior to handling direct submission in
order to avoid the nesting of spinlocks and lift process_csb() and the
majority of the tasklet out of irq-off. However, we do want to avoid
ksoftirqd latency in the fast path, so try and pull the interrupt-bh
local to direct submission if we can acquire the tasklet's lock.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Francisco Jerez <currojerez@xxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_lrc.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index f09dd87324b9..996554766aa5 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -2884,6 +2884,11 @@ static void queue_request(struct intel_engine_cs *engine,
set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
}
+static bool pending_csb(const struct intel_engine_execlists *execlists)
+{
+ return READ_ONCE(*execlists->csb_write) != execlists->csb_head;
+}
+
static void __submit_queue_imm(struct intel_engine_cs *engine)
{
struct intel_engine_execlists * const execlists = &engine->execlists;
@@ -2891,10 +2896,19 @@ static void __submit_queue_imm(struct intel_engine_cs *engine)
if (reset_in_progress(execlists))
return; /* defer until we restart the engine following reset */
- if (execlists->tasklet.func == execlists_submission_tasklet)
- __execlists_submission_tasklet(engine);
- else
- tasklet_hi_schedule(&execlists->tasklet);
+ /* Hopefully we clear execlists->pending[] to let us through */
+ if (execlists->pending[0] && tasklet_trylock(&execlists->tasklet)) {
+ process_csb(engine);
+ tasklet_unlock(&execlists->tasklet);
+ }
+
+ __execlists_submission_tasklet(engine);
+
+ /* Try and pull an interrupt-bh queued on another CPU to here */
+ if (pending_csb(execlists) && tasklet_trylock(&execlists->tasklet)) {
+ process_csb(engine);
+ tasklet_unlock(&execlists->tasklet);
+ }
}
static void submit_queue(struct intel_engine_cs *engine,
--
2.20.1
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