• Chris Wilson's avatar
    drm/i915: Replace execbuf vma ht with an idr · d1b48c1e
    Chris Wilson authored
    This was the competing idea long ago, but it was only with the rewrite
    of the idr as an radixtree and using the radixtree directly ourselves,
    along with the realisation that we can store the vma directly in the
    radixtree and only need a list for the reverse mapping, that made the
    patch performant enough to displace using a hashtable. Though the vma ht
    is fast and doesn't require any extra allocation (as we can embed the node
    inside the vma), it does require a thread for resizing and serialization
    and will have the occasional slow lookup. That is hairy enough to
    investigate alternatives and favour them if equivalent in peak performance.
    One advantage of allocating an indirection entry is that we can support a
    single shared bo between many clients, something that was done on a
    first-come first-serve basis for shared GGTT vma previously. To offset
    the extra allocations, we create yet another kmem_cache for them.
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20170816085210.4199-5-chris@chris-wilson.co.uk
    d1b48c1e
i915_vma.c 18.9 KB