Re: [PATCH 4/4] drm/i915: Emit dma-fence (and execlists submit) first from signaler

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 21/01/2017 09:28, Chris Wilson wrote:
> When introduced, I thought that reducing client latency from the
> signaler was the priority. Since its inception the signaler has become
> responsible for keeping the execlists full, via the dma-fence. As this
> is very important to minimise overall execution time, signal the
> dma-fence first and then signal any waiting clients.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_breadcrumbs.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> index fcfa423d08bd..c1f3bd2e053b 100644
> --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
> +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> @@ -459,16 +459,16 @@ static int intel_breadcrumbs_signaler(void *arg)
>  		 */
>  		request = READ_ONCE(b->first_signal);
>  		if (signal_complete(request)) {
> +			local_bh_disable();
> +			dma_fence_signal(&request->fence);
> +			local_bh_enable(); /* kick start the tasklets */
> +
>  			/* Wake up all other completed waiters and select the
>  			 * next bottom-half for the next user interrupt.
>  			 */
>  			intel_engine_remove_wait(engine,
>  						 &request->signaling.wait);
>
> -			local_bh_disable();
> -			dma_fence_signal(&request->fence);
> -			local_bh_enable(); /* kick start the tasklets */
> -
>  			/* Find the next oldest signal. Note that as we have
>  			 * not been holding the lock, another client may
>  			 * have installed an even older signal than the one
>

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

Regards,

Tvrtko
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