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Commit ed13033f authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/cmdparser: Only cache the dst vmap 



For simplicity, we want to continue using a contiguous mapping of the
command buffer, but we can reduce the number of vmappings we hold by
switching over to a page-by-page copy from the user batch buffer to the
shadow. The cost for saving one linear mapping is about 5% in trivial
workloads - which is more or less the overhead in calling kmap_atomic().

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-34-chris@chris-wilson.co.uk
parent 0b537272

drivers/gpu/drm/i915/i915_cmd_parser.c

+19 −14
Original line number Diff line number Diff line
@@ -946,7 +946,8 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj, 
{

	unsigned int src_needs_clflush;

	unsigned int dst_needs_clflush;

	void *src, *dst;

	void *dst, *ptr;

	int offset, n;

	int ret;



	ret = i915_gem_obj_prepare_shmem_read(src_obj, &src_needs_clflush);
@@ -959,19 +960,12 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj, 
		goto unpin_src;

	}



	src = i915_gem_object_pin_map(src_obj, I915_MAP_WB);

	if (IS_ERR(src)) {

		dst = src;

		goto unpin_dst;

	}



	dst = i915_gem_object_pin_map(dst_obj, I915_MAP_WB);

	if (IS_ERR(dst))

		goto unmap_src;

		goto unpin_dst;



	src += batch_start_offset;

	if (src_needs_clflush)

		drm_clflush_virt_range(src, batch_len);

	ptr = dst;

	offset = offset_in_page(batch_start_offset);



	/* We can avoid clflushing partial cachelines before the write if we

	 * only every write full cache-lines. Since we know that both the
@@ -982,13 +976,24 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj, 
	if (dst_needs_clflush & CLFLUSH_BEFORE)

		batch_len = roundup(batch_len, boot_cpu_data.x86_clflush_size);



	memcpy(dst, src, batch_len);

	for (n = batch_start_offset >> PAGE_SHIFT; batch_len; n++) {

		int len = min_t(int, batch_len, PAGE_SIZE - offset);

		void *vaddr;



		vaddr = kmap_atomic(i915_gem_object_get_page(src_obj, n));

		if (src_needs_clflush)

			drm_clflush_virt_range(vaddr + offset, len);

		memcpy(ptr, vaddr + offset, len);

		kunmap_atomic(vaddr);



		ptr += len;

		batch_len -= len;

		offset = 0;

	}



	/* dst_obj is returned with vmap pinned */

	*needs_clflush_after = dst_needs_clflush & CLFLUSH_AFTER;



unmap_src:

	i915_gem_object_unpin_map(src_obj);

unpin_dst:

	i915_gem_obj_finish_shmem_access(dst_obj);

unpin_src: