[PATCH 3/4] wined3d: Keep track of whether a BO is persistently mapped in a per-BO field.

[Henri Verbeet]

On Mon, 31 Jan 2022 at 18:22, Zebediah Figura <zfigura at codeweavers.com> wrote:
> On 1/31/22 08:11, Henri Verbeet wrote:
> > On Mon, 31 Jan 2022 at 04:05, Zebediah Figura <zfigura at codeweavers.com> wrote:
> >> The ultimate idea being to set a cap on the amount of persistent BO memory, in
> >> which case we need to arbitrarily mark BOs as persistent.
> >>
> > Could the "arbitrary" part be avoided? In particular, what would
> > prevent us from unmapping less recently used mappings when we run into
> > the cap?
>
> Nothing, really. We could relatively easily use an LRU list, or
> periodically garbage-collect unused mappings, for two possibilities.
>
> I think it's a bit orthogonal to this patch, though. No matter what
> criteria we use to determine whether a mapping is persistent in
> wined3d_bo_*_map(), or to possibly unmap it later, we'll at least want
> some of these users of bo->persistent.
>
> I'm also inclined to argue there's no reason not to accept 4/4 now, and
> later (assuming we need to) implement a more complex and optimized
> scheme on top of that. Although it could probably do with a bit more
> factored out into the "adjust_mapped_memory" helpers.

To some extent, yes. However, the follow-up question then becomes what
the "persistent" field really means. Or put a different way, under
what circumstances should we use "bo->persistent" instead of
"bo->map_ptr"?