[Intel-gfx] [PATCH 1/3] drm/i915: Unbind the bo if the user requests a different alignment

[Daniel Vetter]

On Wed, Apr 14, 2010 at 10:29:24AM +0100, Chris Wilson wrote:
> Darn. The current incarnation was literally for glyph masks, clip masks
> and all the other short-lived write-once, immediately use as source
> buffers within the same batch, and then discard. But there is nothing to
> ensure that they exist only within a batch, and so they could well fall
> foul of a17. I wonder if we can simply lazily rebind the bo at the point
> of fence allocation rather than at tiling change. I am not sure if that
> even makes sense yet. The other approach would seem to be to SET_TILING
> on the last use within a batch and hope that doesn't cause a stall. Maybe
> also a mechanism to mark the buffer contents as uninitialized so that if
> we need to unbind, we can simply discard and allocate fresh pages? (An
> extension to madvise, MADV_UNINITIALIZED or MADV_CLEAN?)

At least currently, set_tiling always stalls when actually changing
something (if the alignment doesn't match or if there's a wrong fence reg
attached to the buffer). btw I think the libdrm bo caching has a bug wrt
to this: It resets tiling parameters before inserting a bo into the cache,
while the bo might still be busy. My first try at a patch a few weeks ago
blew up tough, so I left it as-is. Comments?
-Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
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