On Fri, Aug 18, 2017 at 03:08:15PM +0100, Chris Wilson wrote:
> During suspend we want to flush out all active contexts and their
> rendering. To do so we queue a request from the kernel's context, once
> we know that request is done, we know the GPU is completely idle. To
> speed up that switch bump the GPU clocks.
>
> Switching to the kernel context prior to idling is also used to enforce
> a barrier before changing OA properties, and when evicting active
> rendering from the global GTT. All cases where we do want to
> race-to-idle.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: David Weinehall <david.weinehall@xxxxxxxxxxxxxxx>
No statistically significant speedup on suspend in our typical
benchmark, but that one doesn't take into account systems in load--it
suspends from idle, and from the description it seems that this patch
would mostly affect systems with load.
But no regression either, so I'm fine with the patch.
Tested-by: David Weinehall <david.weinehall@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem_context.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index 58a2a44f88bd..ca1423ad2708 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -895,6 +895,7 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
>
> for_each_engine(engine, dev_priv, id) {
> struct drm_i915_gem_request *req;
> + bool active = false;
> int ret;
>
> if (engine_has_kernel_context(engine))
> @@ -913,13 +914,17 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
> prev = i915_gem_active_raw(&tl->last_request,
> &dev_priv->drm.struct_mutex);
> if (prev)
> - i915_sw_fence_await_sw_fence_gfp(&req->submit,
> - &prev->submit,
> - GFP_KERNEL);
> + active |= i915_sw_fence_await_sw_fence_gfp(&req->submit,
> + &prev->submit,
> + GFP_KERNEL) > 0;
> }
>
> ret = i915_switch_context(req);
> +
> + if (active)
> + gen6_rps_boost(req, NULL);
> i915_add_request(req);
> +
> if (ret)
> return ret;
> }
> --
> 2.14.1
>
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