Re: [PATCH] drm/i915/guc: Defer LRC context unpin or release

Yu Dai
2015-11-06T22:04:46Z

Sorry for wrong patch. Please forget about his one. Another one will be
submitted.

Alex

On 11/06/2015 01:56 PM, yu.dai@intel.com wrote:
> From: Alex Dai <yu.dai@intel.com>
>
> Can't immediately free LRC context (neither unpin it) even all
> its referenced requests are completed, because HW still need a
> short period of time to save data to LRC status page. It is safe
> to free LRC when HW completes a request from a different LRC.
>
> Move LRC to ring->last_unpin_ctx when its pin count reaches zero.
> Increase ctx refcount to make sure it won't be freed immediately.
> When HW complete the next request from a different LRC, release
> the last yet-to-be-released one. In the case it is pinned again,
> simply decrease its refcount.
>
> Signed-off-by: Alex Dai <yu.dai@intel.com>
> ---
> drivers/gpu/drm/i915/intel_lrc.c | 54 ++++++++++++++++++++++++++++-----
> drivers/gpu/drm/i915/intel_ringbuffer.h | 1 +
> 2 files changed, 47 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 06180dc..da01d72 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1051,6 +1051,14 @@ static int intel_lr_context_pin(struct drm_i915_gem_request *rq)
> if (ret)
> goto reset_pin_count;
> }
> +
> + /* If we are holding this LRC from last unpin, unref it here. */
> + if (ring->last_unpin_ctx == rq->ctx) {
> + rq->ctx->engine[ring->id].pin_count--;
> + i915_gem_context_unreference(rq->ctx);
> + ring->last_unpin_ctx = NULL;
> + }
> +
> return ret;
>
> reset_pin_count:
> @@ -1058,18 +1066,46 @@ reset_pin_count:
> return ret;
> }
>
> +static void
> +lrc_unpin_last_ctx(struct intel_engine_cs *ring)
> +{
> + struct intel_context *ctx = ring->last_unpin_ctx;
> + struct drm_i915_gem_object *ctx_obj;
> +
> + if (!ctx)
> + return;
> +
> + i915_gem_object_ggtt_unpin(ctx->engine[ring->id].state);
> + intel_unpin_ringbuffer_obj(ctx->engine[ring->id].ringbuf);
> +
> + WARN_ON(--ctx->engine[ring->id].pin_count);
> + i915_gem_context_unreference(ctx);
> +
> + ring->last_unpin_ctx = NULL;
> +}
> +
> void intel_lr_context_unpin(struct drm_i915_gem_request *rq)
> {
> struct intel_engine_cs *ring = rq->ring;
> - struct drm_i915_gem_object *ctx_obj = rq->ctx->engine[ring->id].state;
> - struct intel_ringbuffer *ringbuf = rq->ringbuf;
>
> - if (ctx_obj) {
> - WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
> - if (--rq->ctx->engine[ring->id].pin_count == 0) {
> - intel_unpin_ringbuffer_obj(ringbuf);
> - i915_gem_object_ggtt_unpin(ctx_obj);
> - }
> + if (!rq->ctx->engine[ring->id].state)
> + return;
> +
> + WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
> +
> + /* HW completes request from a different LRC, unpin the last one. */
> + if (ring->last_unpin_ctx != rq->ctx)
> + lrc_unpin_last_ctx(ring);
> +
> + if (--rq->ctx->engine[ring->id].pin_count == 0) {
> + /* Last one should be unpined already */
> + WARN_ON(ring->last_unpin_ctx);
> +
> + /* Keep the context pinned and ref-counted */
> + rq->ctx->engine[ring->id].pin_count++;
> + i915_gem_context_reference(rq->ctx);
> +
> + ring->last_unpin_ctx = rq->ctx;
> }
> }
>
> @@ -1908,6 +1944,8 @@ void intel_logical_ring_cleanup(struct intel_engine_cs *ring)
> }
>
> lrc_destroy_wa_ctx_obj(ring);
> +
> + lrc_unpin_last_ctx(ring);
> }
>
> static int logical_ring_init(struct drm_device *dev, struct intel_engine_cs *ring)
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 58b1976..676d27f 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -267,6 +267,7 @@ struct intel_engine_cs {
> spinlock_t execlist_lock;
> struct list_head execlist_queue;
> struct list_head execlist_retired_req_list;
> + struct intel_context *last_unpin_ctx;
> u8 next_context_status_buffer;
> u32 irq_keep_mask; /* bitmask for interrupts that should not be masked */
> int (*emit_request)(struct drm_i915_gem_request *request);