On Tue, Apr 19, 2016 at 06:40:07PM +0100, Dave Gordon wrote:
> From: Alex Dai <yu.dai@xxxxxxxxx>
>
> The recently-added i915_gem_object_pin_map() can be further optimised
> for "small" objects. To facilitate this, and simplify the error paths
> before adding the new code, this patch pulls out the "mapping" part of
> the operation (involving local allocations which must be undone before
> return) into its own subfunction.
>
> The next patch will then insert the new optimisation into the middle of
> the now-separated subfunction.
>
> This reorganisation will probably not affect the generated code, as the
> compiler will most likely inline it anyway, but it makes the logical
> structure a bit clearer and easier to modify.
>
> Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 61 +++++++++++++++++++++++++++--------------
> 1 file changed, 40 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 6ce2c31..fc42be0 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2396,6 +2396,45 @@ static void i915_gem_object_free_mmap_offset(struct drm_i915_gem_object *obj)
> return 0;
> }
>
> +/* The 'mapping' part of i915_gem_object_pin_map() below */
> +static void *i915_gem_object_map(const struct drm_i915_gem_object *obj)
> +{
> + unsigned long n_pages = obj->base.size >> PAGE_SHIFT;
> + struct scatterlist *sg = obj->pages->sgl;
> + struct sg_page_iter sg_iter;
> + struct page **pages;
> + unsigned long i = 0;
> + void *addr = NULL;
> +
> + /* A single page can always be kmapped */
> + if (n_pages == 1)
> + return kmap(sg_page(sg));
> +
> + pages = drm_malloc_gfp(n_pages, sizeof(*pages), GFP_TEMPORARY);
> + if (pages == NULL) {
> + DRM_DEBUG_DRIVER("Failed to get space for pages\n");
> + return NULL;
> + }
> +
> + for_each_sg_page(sg, &sg_iter, n_pages, 0) {
> + pages[i] = sg_page_iter_page(&sg_iter);
Just pages[i++] = sg_page_iter_page(&sg_iter);
> + if (++i == n_pages) {
> + addr = vmap(pages, n_pages, 0, PAGE_KERNEL);
> + break;
> + }
> + }
> +
> + /* We should have got here via the 'break' above */
> + WARN_ON(i != n_pages);
> + if (addr == NULL)
> + DRM_DEBUG_DRIVER("Failed to vmap pages\n");
As this is a very, very confused loop.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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