drm/i915: Store a direct lookup from object handle to vma
The advent of full-ppgtt lead to an extra indirection between the object and its binding. That extra indirection has a noticeable impact on how fast we can convert from the user handles to our internal vma for execbuffer. In order to bypass the extra indirection, we use a resizable hashtable to jump from the object to the per-ctx vma. rhashtable was considered but we don't need the online resizing feature and the extra complexity proved to undermine its usefulness. Instead, we simply reallocate the hastable on demand in a background task and serialize it before iterating. In non-full-ppgtt modes, multiple files and multiple contexts can share the same vma. This leads to having multiple possible handle->vma links, so we only use the first to establish the fast path. The majority of buffers are not shared and so we should still be able to realise speedups with multiple clients. v2: Prettier names, more magic. v3: Many style tweaks, most notably hiding the misuse of execobj[].rsvd2 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
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