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drm/i915/cmdparser: Only cache the dst vmap

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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
This commit is contained in:
Chris Wilson 2016-08-18 17:17:13 +01:00
parent 0b5372727b
commit ed13033f02
1 changed files with 19 additions and 14 deletions
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33
drivers/gpu/drm/i915/i915_cmd_parser.c
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@ -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: