linux-kernel - Re: [PATCH 1/2 RESEND] drm/vc4: Fulfill user BO creation requests from the kernel BO cache.

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Message-ID: <20170302090809.104c1dac@bbrezillon>
Date:   Thu, 2 Mar 2017 09:08:09 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2 RESEND] drm/vc4: Fulfill user BO creation requests
 from the kernel BO cache.

On Wed,  1 Mar 2017 10:56:01 -0800
Eric Anholt <eric@...olt.net> wrote:

> The from_cache flag was actually "the BO is invisible to userspace",
> so we can repurpose it to just zero out a cached BO and return it to
> userspace.
> 
> Improves wall time for a loop of 5 glsl-algebraic-add-add-1 by
> -1.44989% +/- 0.862891% (n=28, 1 outlier removed from each that
> appeared to be other system noise)
> 
> Note that there's an intel-gpu-tools test to check for the proper
> zeroing behavior here, which we continue to pass.
> 
> Signed-off-by: Eric Anholt <eric@...olt.net>

Reviewed-by: Boris Brezillon <boris.brezillon@...e-electrons.com>

> ---
>  drivers/gpu/drm/vc4/vc4_bo.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c
> index 7abcd9c5dbe2..e5c7aa935b4b 100644
> --- a/drivers/gpu/drm/vc4/vc4_bo.c
> +++ b/drivers/gpu/drm/vc4/vc4_bo.c
> @@ -211,21 +211,22 @@ struct drm_gem_object *vc4_create_object(struct drm_device *dev, size_t size)
>  }
>  
>  struct vc4_bo *vc4_bo_create(struct drm_device *dev, size_t unaligned_size,
> -			     bool from_cache)
> +			     bool allow_unzeroed)
>  {
>  	size_t size = roundup(unaligned_size, PAGE_SIZE);
>  	struct vc4_dev *vc4 = to_vc4_dev(dev);
>  	struct drm_gem_cma_object *cma_obj;
> +	struct vc4_bo *bo;
>  
>  	if (size == 0)
>  		return ERR_PTR(-EINVAL);
>  
>  	/* First, try to get a vc4_bo from the kernel BO cache. */
> -	if (from_cache) {
> -		struct vc4_bo *bo = vc4_bo_get_from_cache(dev, size);
> -
> -		if (bo)
> -			return bo;
> +	bo = vc4_bo_get_from_cache(dev, size);
> +	if (bo) {
> +		if (!allow_unzeroed)
> +			memset(bo->base.vaddr, 0, bo->base.base.size);
> +		return bo;
>  	}
>  
>  	cma_obj = drm_gem_cma_create(dev, size);