On Sun, Mar 25, 2012 at 07:47:34PM +0200, Daniel Vetter wrote:
> This speeds up pwrite and pread from ~120 ?s ro ~100 ?s for
> reading/writing 1mb on my snb (if the backing storage pages
> are already pinned, of course).
>
> v2: Chris Wilson pointed out a claring page reference bug - I've
s/claring/glaring, noticed by Chris.
Note to self: Fix this when applying.
-Daniel
> unconditionally dropped the reference. With that fixed (and the
> associated reduction of dirt in dmesg) it's now even a notch faster.
>
> v3: Unconditionaly grab a page reference when dropping
> dev->struct_mutex to simplify the code-flow.
>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 42 +++++++++++++++++++++++++++-----------
> 1 files changed, 30 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c5b250c..117fda4 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -321,6 +321,7 @@ i915_gem_shmem_pread(struct drm_device *dev,
> int obj_do_bit17_swizzling, page_do_bit17_swizzling;
> int hit_slowpath = 0;
> int needs_clflush = 0;
> + int release_page;
>
> user_data = (char __user *) (uintptr_t) args->data_ptr;
> remain = args->size;
> @@ -355,10 +356,16 @@ i915_gem_shmem_pread(struct drm_device *dev,
> if ((shmem_page_offset + page_length) > PAGE_SIZE)
> page_length = PAGE_SIZE - shmem_page_offset;
>
> - page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
> - if (IS_ERR(page)) {
> - ret = PTR_ERR(page);
> - goto out;
> + if (obj->pages) {
> + page = obj->pages[offset >> PAGE_SHIFT];
> + release_page = 0;
> + } else {
> + page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
> + if (IS_ERR(page)) {
> + ret = PTR_ERR(page);
> + goto out;
> + }
> + release_page = 1;
> }
>
> page_do_bit17_swizzling = obj_do_bit17_swizzling &&
> @@ -378,7 +385,7 @@ i915_gem_shmem_pread(struct drm_device *dev,
> }
>
> hit_slowpath = 1;
> -
> + page_cache_get(page);
> mutex_unlock(&dev->struct_mutex);
>
> vaddr = kmap(page);
> @@ -397,9 +404,11 @@ i915_gem_shmem_pread(struct drm_device *dev,
> kunmap(page);
>
> mutex_lock(&dev->struct_mutex);
> + page_cache_release(page);
> next_page:
> mark_page_accessed(page);
> - page_cache_release(page);
> + if (release_page)
> + page_cache_release(page);
>
> if (ret) {
> ret = -EFAULT;
> @@ -680,6 +689,7 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
> int shmem_page_offset, page_length, ret = 0;
> int obj_do_bit17_swizzling, page_do_bit17_swizzling;
> int hit_slowpath = 0;
> + int release_page;
>
> user_data = (char __user *) (uintptr_t) args->data_ptr;
> remain = args->size;
> @@ -704,10 +714,16 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
> if ((shmem_page_offset + page_length) > PAGE_SIZE)
> page_length = PAGE_SIZE - shmem_page_offset;
>
> - page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
> - if (IS_ERR(page)) {
> - ret = PTR_ERR(page);
> - goto out;
> + if (obj->pages) {
> + page = obj->pages[offset >> PAGE_SHIFT];
> + release_page = 0;
> + } else {
> + page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
> + if (IS_ERR(page)) {
> + ret = PTR_ERR(page);
> + goto out;
> + }
> + release_page = 1;
> }
>
> page_do_bit17_swizzling = obj_do_bit17_swizzling &&
> @@ -725,7 +741,7 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
> }
>
> hit_slowpath = 1;
> -
> + page_cache_get(page);
> mutex_unlock(&dev->struct_mutex);
>
> vaddr = kmap(page);
> @@ -740,10 +756,12 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
> kunmap(page);
>
> mutex_lock(&dev->struct_mutex);
> + page_cache_release(page);
> next_page:
> set_page_dirty(page);
> mark_page_accessed(page);
> - page_cache_release(page);
> + if (release_page)
> + page_cache_release(page);
>
> if (ret) {
> ret = -EFAULT;
> --
> 1.7.7.6
>
--
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48
