[Intel-gfx] [PATCH 7/9] drm/i915/execlists: Reduce lock context between schedule/submit_request

[Chris Wilson]

s/context/contention/ in subject

On Wed, May 03, 2017 at 12:37:57PM +0100, Chris Wilson wrote:
> If we do not require to perform priority bumping, and we haven't yet
> submitted the request, we can update its priority in situ and skip
> acquiring the engine locks -- thus avoiding any contention between us
> and submit/execute.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index fb0025627676..ca7f28795e2d 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -767,6 +767,17 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio)
>  		list_safe_reset_next(dep, p, dfs_link);
>  	}
>  
> +	/* If we didn't need to bump any existing priorites, and we haven't
> +	 * yet submitted this request (i..e there is no porential race with
> +	 * execlists_submit_request()), we can set our own priority and skip
> +	 * acquiring the engine locks.
> +	 */
> +	if (request->priotree.priority == INT_MIN) {
> +		request->priotree.priority = prio;
> +		if (stack.dfs_link.next == stack.dfs_link.prev)
> +			return;
> +	}
> +
>  	engine = request->engine;
>  	spin_lock_irq(&engine->timeline->lock);
>  
> -- 
> 2.11.0
> 

-- 
Chris Wilson, Intel Open Source Technology Centre