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: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Matthew Auld <matthew.auld@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-34-chris@chris-wilson.co.uk
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0b5372727b
Коммит
ed13033f02
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@ -946,7 +946,8 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj,
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{
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unsigned int src_needs_clflush;
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unsigned int dst_needs_clflush;
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void *src, *dst;
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void *dst, *ptr;
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int offset, n;
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int ret;
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ret = i915_gem_obj_prepare_shmem_read(src_obj, &src_needs_clflush);
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@ -959,19 +960,12 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj,
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goto unpin_src;
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}
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src = i915_gem_object_pin_map(src_obj, I915_MAP_WB);
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if (IS_ERR(src)) {
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dst = src;
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goto unpin_dst;
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}
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dst = i915_gem_object_pin_map(dst_obj, I915_MAP_WB);
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if (IS_ERR(dst))
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goto unmap_src;
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goto unpin_dst;
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src += batch_start_offset;
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if (src_needs_clflush)
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drm_clflush_virt_range(src, batch_len);
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ptr = dst;
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offset = offset_in_page(batch_start_offset);
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/* We can avoid clflushing partial cachelines before the write if we
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* only every write full cache-lines. Since we know that both the
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@ -982,13 +976,24 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj,
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if (dst_needs_clflush & CLFLUSH_BEFORE)
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batch_len = roundup(batch_len, boot_cpu_data.x86_clflush_size);
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memcpy(dst, src, batch_len);
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for (n = batch_start_offset >> PAGE_SHIFT; batch_len; n++) {
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int len = min_t(int, batch_len, PAGE_SIZE - offset);
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void *vaddr;
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vaddr = kmap_atomic(i915_gem_object_get_page(src_obj, n));
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if (src_needs_clflush)
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drm_clflush_virt_range(vaddr + offset, len);
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memcpy(ptr, vaddr + offset, len);
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kunmap_atomic(vaddr);
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ptr += len;
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batch_len -= len;
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offset = 0;
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}
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/* dst_obj is returned with vmap pinned */
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*needs_clflush_after = dst_needs_clflush & CLFLUSH_AFTER;
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unmap_src:
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i915_gem_object_unpin_map(src_obj);
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unpin_dst:
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i915_gem_obj_finish_shmem_access(dst_obj);
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unpin_src:
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