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drm/i915: Reduce i915_request.lock contention for i915_request_wait

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Currently, we use i915_request_completed() directly in
i915_request_wait() and follow up with a manual invocation of
dma_fence_signal(). This appears to cause a large number of contentions
on i915_request.lock as when the process is woken up after the fence is
signaled by an interrupt, we will then try and call dma_fence_signal()
ourselves while the signaler is still holding the lock.
dma_fence_is_signaled() has the benefit of checking the
DMA_FENCE_FLAG_SIGNALED_BIT prior to calling dma_fence_signal() and so
avoids most of that contention.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200716100754.5670-1-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
This commit is contained in:
Chris Wilson
2020-07-16 11:07:54 +01:00
committed by Joonas Lahtinen
parent 3393649977
commit 3f6a6f343c
1 changed files with 8 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
drivers/gpu/drm/i915/i915_request.c
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@@ -1640,7 +1640,7 @@ static bool busywait_stop(unsigned long timeout, unsigned int cpu)
return this_cpu != cpu;
}
static bool __i915_spin_request(const struct i915_request * const rq, int state)
static bool __i915_spin_request(struct i915_request * const rq, int state)
{
unsigned long timeout_ns;
unsigned int cpu;
@@ -1673,7 +1673,7 @@ static bool __i915_spin_request(const struct i915_request * const rq, int state)
timeout_ns = READ_ONCE(rq->engine->props.max_busywait_duration_ns);
timeout_ns += local_clock_ns(&cpu);
do {
if (i915_request_completed(rq))
if (dma_fence_is_signaled(&rq->fence))
return true;
if (signal_pending_state(state, current))
@@ -1697,7 +1697,7 @@ static void request_wait_wake(struct dma_fence *fence, struct dma_fence_cb *cb)
{
struct request_wait *wait = container_of(cb, typeof(*wait), cb);
wake_up_process(wait->tsk);
wake_up_process(fetch_and_zero(&wait->tsk));
}
/**
@@ -1766,10 +1766,8 @@ long i915_request_wait(struct i915_request *rq,
* duration, which we currently lack.
*/
if (IS_ACTIVE(CONFIG_DRM_I915_MAX_REQUEST_BUSYWAIT) &&
__i915_spin_request(rq, state)) {
dma_fence_signal(&rq->fence);
__i915_spin_request(rq, state))
goto out;
}
/*
* This client is about to stall waiting for the GPU. In many cases
@@ -1793,10 +1791,8 @@ long i915_request_wait(struct i915_request *rq,
for (;;) {
set_current_state(state);
if (i915_request_completed(rq)) {
dma_fence_signal(&rq->fence);
if (dma_fence_is_signaled(&rq->fence))
break;
}
intel_engine_flush_submission(rq->engine);
@@ -1814,7 +1810,9 @@ long i915_request_wait(struct i915_request *rq,
}
__set_current_state(TASK_RUNNING);
dma_fence_remove_callback(&rq->fence, &wait.cb);
if (READ_ONCE(wait.tsk))
dma_fence_remove_callback(&rq->fence, &wait.cb);
GEM_BUG_ON(!list_empty(&wait.cb.node));
out:
mutex_release(&rq->engine->gt->reset.mutex.dep_map, _THIS_IP_);