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drm/i915: don't call shmem_read_mapping unnecessarily 

This speeds up pwrite and pread from ~120 µs ro ~100 µs for
reading/writing 1mb on my snb (if the backing storage pages
are already pinned, of course).

v2: Chris Wilson pointed out a glaring page reference bug - I've
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.

Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
hifive-unleashed-5.1
Daniel Vetter 2012-03-25 19:47:34 +02:00
parent 3ae5378330
commit 692a576b9d
1 changed files with 30 additions and 12 deletions
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42
drivers/gpu/drm/i915/i915_gem.c
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@ -301,6 +301,7 @@ 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;
@ -335,10 +336,16 @@ 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 &&
@ -358,7 +365,7 @@ i915_gem_shmem_pread(struct drm_device *dev,
}
hit_slowpath = 1;
page_cache_get(page);
mutex_unlock(&dev->struct_mutex);
vaddr = kmap(page);
@ -377,9 +384,11 @@ 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;
@ -660,6 +669,7 @@ 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;
@ -684,10 +694,16 @@ 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 &&
@ -705,7 +721,7 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
}
hit_slowpath = 1;
page_cache_get(page);
mutex_unlock(&dev->struct_mutex);
vaddr = kmap(page);
@ -720,10 +736,12 @@ 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;