Re: [PATCH 33/43] drm/i915/bdw: Help out the ctx switch interrupt handler

Daniel Vetter
2014-08-14T20:43:04Z

On Thu, Jul 24, 2014 at 05:04:41PM +0100, Thomas Daniel wrote:
> From: Oscar Mateo <oscar.mateo@intel.com>
>
> If we receive a storm of requests for the same context (see gem_storedw_loop_*)
> we might end up iterating over too many elements in interrupt time, looking for
> contexts to squash together. Instead, share the burden by giving more
> intelligence to the queue function. At most, the interrupt will iterate over
> three elements.
>
> Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>

I'll continue merging after this patch tomorrow.
-Daniel

> ---
> drivers/gpu/drm/i915/intel_lrc.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 895dbfc..829b15d 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -384,9 +384,10 @@ static int execlists_context_queue(struct intel_engine_cs *ring,
> struct intel_context *to,
> u32 tail)
> {
> - struct intel_ctx_submit_request *req = NULL;
> + struct drm_i915_private *dev_priv = ring->dev->dev_private;
> + struct intel_ctx_submit_request *req = NULL, *cursor;
> unsigned long flags;
> - bool was_empty;
> + int num_elements = 0;
>
> req = kzalloc(sizeof(*req), GFP_KERNEL);
> if (req == NULL)
> @@ -400,9 +401,26 @@ static int execlists_context_queue(struct intel_engine_cs *ring,
>
> spin_lock_irqsave(&ring->execlist_lock, flags);
>
> - was_empty = list_empty(&ring->execlist_queue);
> + list_for_each_entry(cursor, &ring->execlist_queue, execlist_link)
> + if (++num_elements > 2)
> + break;
> +
> + if (num_elements > 2) {
> + struct intel_ctx_submit_request *tail_req;
> +
> + tail_req = list_last_entry(&ring->execlist_queue,
> + struct intel_ctx_submit_request,
> + execlist_link);
> + if (to == tail_req->ctx) {
> + WARN(tail_req->elsp_submitted != 0,
> + "More than 2 already-submitted reqs queued\n");
> + list_del(&tail_req->execlist_link);
> + queue_work(dev_priv->wq, &tail_req->work);
> + }
> + }
> +
> list_add_tail(&req->execlist_link, &ring->execlist_queue);
> - if (was_empty)
> + if (num_elements == 0)
> execlists_context_unqueue(ring);
>
> spin_unlock_irqrestore(&ring->execlist_lock, flags);
> --
> 1.7.9.5
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch