[1/2] drm/i915/execlists: Pull tasklet interrupt-bh local to direct submission
diff mbox series

Message ID 20200325120227.8044-1-chris@chris-wilson.co.uk
State New
Headers show
Series
  • [1/2] drm/i915/execlists: Pull tasklet interrupt-bh local to direct submission
Related show

Commit Message

Chris Wilson March 25, 2020, 12:02 p.m. UTC
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.

v2: Document the read of pending[0] from outside the tasklet with
READ_ONCE.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Tvrtko Ursulin March 25, 2020, 12:56 p.m. UTC | #1
On 25/03/2020 12:02, Chris Wilson wrote:
> 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.
> 
> v2: Document the read of pending[0] from outside the tasklet with
> READ_ONCE.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> ---
>   drivers/gpu/drm/i915/gt/intel_lrc.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index f88d3b95c4e1..d49baade0986 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -2891,6 +2891,13 @@ static void __submit_queue_imm(struct intel_engine_cs *engine)
>   	if (reset_in_progress(execlists))
>   		return; /* defer until we restart the engine following reset */
>   
> +	/* Hopefully we clear execlists->pending[] to let us through */
> +	if (READ_ONCE(execlists->pending[0]) &&
> +	    tasklet_trylock(&execlists->tasklet)) {
> +		process_csb(engine);
> +		tasklet_unlock(&execlists->tasklet);
> +	}
> +
>   	__execlists_submission_tasklet(engine);
>   }
>   
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index f88d3b95c4e1..d49baade0986 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -2891,6 +2891,13 @@  static void __submit_queue_imm(struct intel_engine_cs *engine)
 	if (reset_in_progress(execlists))
 		return; /* defer until we restart the engine following reset */
 
+	/* Hopefully we clear execlists->pending[] to let us through */
+	if (READ_ONCE(execlists->pending[0]) &&
+	    tasklet_trylock(&execlists->tasklet)) {
+		process_csb(engine);
+		tasklet_unlock(&execlists->tasklet);
+	}
+
 	__execlists_submission_tasklet(engine);
 }