Re: [PATCH v2 6/6] drm/i915: Avoid allocating a vmap arena for a single page

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 08/04/16 12:11, Chris Wilson wrote:
> If we want a contiguous mapping of a single page sized object, we can
> forgo using vmap() and just use a regular kmap(). Note that this is only
> suitable if the desired pgprot_t is compatible.
>
> v2: Use is_vmalloc_addr()
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: Dave Gordon <david.s.gordon@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 19 ++++++++++++++-----
>   1 file changed, 14 insertions(+), 5 deletions(-)

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko

> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index fa810226bd8b..b37ffea8b458 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2233,7 +2233,10 @@ i915_gem_object_put_pages(struct drm_i915_gem_object *obj)
>   	list_del(&obj->global_list);
>
>   	if (obj->mapping) {
> -		vunmap(obj->mapping);
> +		if (is_vmalloc_addr(obj->mapping))
> +			vunmap(obj->mapping);
> +		else
> +			kunmap(kmap_to_page(obj->mapping));
>   		obj->mapping = NULL;
>   	}
>
> @@ -2418,13 +2421,19 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj)
>   	i915_gem_object_pin_pages(obj);
>
>   	if (obj->mapping == NULL) {
> -		struct sg_page_iter sg_iter;
>   		struct page **pages;
> -		int n;
>
> -		n = obj->base.size >> PAGE_SHIFT;
> -		pages = drm_malloc_gfp(n, sizeof(*pages), GFP_TEMPORARY);
> +		pages = NULL;
> +		if (obj->base.size == PAGE_SIZE)
> +			obj->mapping = kmap(sg_page(obj->pages->sgl));
> +		else
> +			pages = drm_malloc_gfp(obj->base.size >> PAGE_SHIFT,
> +					       sizeof(*pages),
> +					       GFP_TEMPORARY);
>   		if (pages != NULL) {
> +			struct sg_page_iter sg_iter;
> +			int n;
> +
>   			n = 0;
>   			for_each_sg_page(obj->pages->sgl, &sg_iter,
>   					 obj->pages->nents, 0)
>
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