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Subject[PATCH 12/13] drm/i915: drop gtt slowpath
Date
With the proper prefault, it's extremely unlikely that we fall back
to the gtt slowpath.

So just kill it and use the shmem_pwrite path as fallback.

To further clean up the code, move the preparatory gem calls into the
respective pwrite functions. This way the gtt_fast->shmem fallback
is much more obvious.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/gpu/drm/i915/i915_gem.c | 183 +++++++--------------------------------
1 files changed, 30 insertions(+), 153 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 5b8a7c5..0a374e1 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -523,30 +523,6 @@ fast_user_write(struct io_mapping *mapping,
return unwritten;
}

-/* Here's the write path which can sleep for
- * page faults
- */
-
-static inline void
-slow_kernel_write(struct io_mapping *mapping,
- loff_t gtt_base, int gtt_offset,
- struct page *user_page, int user_offset,
- int length)
-{
- char __iomem *dst_vaddr;
- char *src_vaddr;
-
- dst_vaddr = io_mapping_map_wc(mapping, gtt_base);
- src_vaddr = kmap(user_page);
-
- memcpy_toio(dst_vaddr + gtt_offset,
- src_vaddr + user_offset,
- length);
-
- kunmap(user_page);
- io_mapping_unmap(dst_vaddr);
-}
-
/**
* This is the fast pwrite path, where we copy the data directly from the
* user into the GTT, uncached.
@@ -561,7 +537,19 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev,
ssize_t remain;
loff_t offset, page_base;
char __user *user_data;
- int page_offset, page_length;
+ int page_offset, page_length, ret;
+
+ ret = i915_gem_object_pin(obj, 0, true);
+ if (ret)
+ goto out;
+
+ ret = i915_gem_object_set_to_gtt_domain(obj, true);
+ if (ret)
+ goto out_unpin;
+
+ ret = i915_gem_object_put_fence(obj);
+ if (ret)
+ goto out_unpin;

user_data = (char __user *) (uintptr_t) args->data_ptr;
remain = args->size;
@@ -586,112 +574,19 @@ i915_gem_gtt_pwrite_fast(struct drm_device *dev,
* retry in the slow path.
*/
if (fast_user_write(dev_priv->mm.gtt_mapping, page_base,
- page_offset, user_data, page_length))
- return -EFAULT;
+ page_offset, user_data, page_length)) {
+ ret = -EFAULT;
+ goto out_unpin;
+ }

remain -= page_length;
user_data += page_length;
offset += page_length;
}

- return 0;
-}
-
-/**
- * This is the fallback GTT pwrite path, which uses get_user_pages to pin
- * the memory and maps it using kmap_atomic for copying.
- *
- * This code resulted in x11perf -rgb10text consuming about 10% more CPU
- * than using i915_gem_gtt_pwrite_fast on a G45 (32-bit).
- */
-static int
-i915_gem_gtt_pwrite_slow(struct drm_device *dev,
- struct drm_i915_gem_object *obj,
- struct drm_i915_gem_pwrite *args,
- struct drm_file *file)
-{
- drm_i915_private_t *dev_priv = dev->dev_private;
- ssize_t remain;
- loff_t gtt_page_base, offset;
- loff_t first_data_page, last_data_page, num_pages;
- loff_t pinned_pages, i;
- struct page **user_pages;
- struct mm_struct *mm = current->mm;
- int gtt_page_offset, data_page_offset, data_page_index, page_length;
- int ret;
- uint64_t data_ptr = args->data_ptr;
-
- remain = args->size;
-
- /* Pin the user pages containing the data. We can't fault while
- * holding the struct mutex, and all of the pwrite implementations
- * want to hold it while dereferencing the user data.
- */
- first_data_page = data_ptr / PAGE_SIZE;
- last_data_page = (data_ptr + args->size - 1) / PAGE_SIZE;
- num_pages = last_data_page - first_data_page + 1;
-
- user_pages = drm_malloc_ab(num_pages, sizeof(struct page *));
- if (user_pages == NULL)
- return -ENOMEM;
-
- mutex_unlock(&dev->struct_mutex);
- down_read(&mm->mmap_sem);
- pinned_pages = get_user_pages(current, mm, (uintptr_t)args->data_ptr,
- num_pages, 0, 0, user_pages, NULL);
- up_read(&mm->mmap_sem);
- mutex_lock(&dev->struct_mutex);
- if (pinned_pages < num_pages) {
- ret = -EFAULT;
- goto out_unpin_pages;
- }
-
- ret = i915_gem_object_set_to_gtt_domain(obj, true);
- if (ret)
- goto out_unpin_pages;
-
- ret = i915_gem_object_put_fence(obj);
- if (ret)
- goto out_unpin_pages;
-
- offset = obj->gtt_offset + args->offset;
-
- while (remain > 0) {
- /* Operation in this page
- *
- * gtt_page_base = page offset within aperture
- * gtt_page_offset = offset within page in aperture
- * data_page_index = page number in get_user_pages return
- * data_page_offset = offset with data_page_index page.
- * page_length = bytes to copy for this page
- */
- gtt_page_base = offset & PAGE_MASK;
- gtt_page_offset = offset_in_page(offset);
- data_page_index = data_ptr / PAGE_SIZE - first_data_page;
- data_page_offset = offset_in_page(data_ptr);
-
- page_length = remain;
- if ((gtt_page_offset + page_length) > PAGE_SIZE)
- page_length = PAGE_SIZE - gtt_page_offset;
- if ((data_page_offset + page_length) > PAGE_SIZE)
- page_length = PAGE_SIZE - data_page_offset;
-
- slow_kernel_write(dev_priv->mm.gtt_mapping,
- gtt_page_base, gtt_page_offset,
- user_pages[data_page_index],
- data_page_offset,
- page_length);
-
- remain -= page_length;
- offset += page_length;
- data_ptr += page_length;
- }
-
-out_unpin_pages:
- for (i = 0; i < pinned_pages; i++)
- page_cache_release(user_pages[i]);
- drm_free_large(user_pages);
-
+out_unpin:
+ i915_gem_object_unpin(obj);
+out:
return ret;
}

@@ -710,6 +605,10 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
int hit_slowpath = 0;
int release_page;

+ ret = i915_gem_object_set_to_cpu_domain(obj, 1);
+ if (ret)
+ return ret;
+
user_data = (char __user *) (uintptr_t) args->data_ptr;
remain = args->size;

@@ -854,6 +753,7 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,

trace_i915_gem_object_pwrite(obj, args->offset, args->size);

+ ret = -EFAULT;
/* We can only do the GTT pwrite on untiled buffers, as otherwise
* it would end up going through the fenced access, and we'll get
* different detiling behavior between reading and writing.
@@ -866,37 +766,14 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
} else if (obj->gtt_space &&
obj->cache_level == I915_CACHE_NONE &&
obj->base.write_domain != I915_GEM_DOMAIN_CPU) {
- ret = i915_gem_object_pin(obj, 0, true);
- if (ret)
- goto out;
-
- ret = i915_gem_object_set_to_gtt_domain(obj, true);
- if (ret)
- goto out_unpin;
-
- ret = i915_gem_object_put_fence(obj);
- if (ret)
- goto out_unpin;
-
ret = i915_gem_gtt_pwrite_fast(dev, obj, args, file);
- if (ret == -EFAULT)
- ret = i915_gem_gtt_pwrite_slow(dev, obj, args, file);
-
-out_unpin:
- i915_gem_object_unpin(obj);
-
- if (ret != -EFAULT)
- goto out;
- /* Fall through to the shmfs paths because the gtt paths might
- * fail with non-page-backed user pointers (e.g. gtt mappings
- * when moving data between textures). */
+ /* Note that the gtt paths might fail with non-page-backed user
+ * pointers (e.g. gtt mappings when moving data between
+ * textures). Fallback to the shmem path in that case. */
}

- ret = i915_gem_object_set_to_cpu_domain(obj, 1);
- if (ret)
- goto out;
-
- ret = i915_gem_shmem_pwrite(dev, obj, args, file);
+ if (ret == -EFAULT)
+ ret = i915_gem_shmem_pwrite(dev, obj, args, file);

out:
drm_gem_object_unreference(&obj->base);
--
1.7.6.4


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