[Mesa-dev] [PATCH 00/12] i965/gen7+: Implement fast color clears.

[Paul Berry]

On 21 May 2013 16:52, Paul Berry <stereotype441 at gmail.com> wrote:

> This series implements fast color clears, a Gen7+ feature which
> reduces memory bandwidth by deferring the memory writes involved in a
> glClear() until the same memory is later touched during rendering.
>
> From a broad overview point of view, fast color clears work in a
> similar way to HiZ: an auxiliary "MCS" buffer keeps track of which
> parts of the buffer have been cleared but haven't yet had the
> necessary memory writes performed.  Whenever a color buffer needs to
> be accessed by the CPU, or by a part of the GPU that is not
> fast-color-aware, we have to perform a "resolve operation" to force
> any pending memory writes to occur.
>
> This patch series adopts a slightly different strategy (compared to
> HiZ) for making sure the resolves happen when needed.  Instead of
> modifying each code path that might need to do a resolve so that it
> does one if needed, we create an accessor function that does the
> resolve if needed and then provides the caller with access to the
> miptree's underlying memory region.  This lets us have a lot more
> confidence that we didn't miss any code paths, which is important
> since color buffers are accessed by a large number of code paths.  To
> discourage future maintainers from trying to bypass the accessor
> function, it is inline (so that overhead is negligible), and the field
> it provides access to has been renamed to region_private.
>
> Patch 01 ifdefs out some code so that it does not appear in the i915
> (pre-Gen4) driver--this makes it easier to be confident that these
> changes won't regress i915.  Patch 02 introduces the aforementioned
> accessor function.  Patches 03-11 are the guts of the implementation,
> and patch 12 enables the new feature.
>
> No piglit regressions.  I have additional piglit tests which validate
> specific important corner cases--I hope to get those out to the list
> later this week.
>
> [PATCH 01/12] intel: Conditionally compile mcs-related code for i965 only.
> [PATCH 02/12] intel: Create intel_miptree_get_region() to prepare for fast
> color clear.
> [PATCH 03/12] i965/gen7+: Create an enum for keeping track of fast color
> clear state.
> [PATCH 04/12] i965/gen7+: Set up MCS in SURFACE_STATE whenever MCS is
> present.
> [PATCH 05/12] i965/gen7+: Create helper functions for single-sample MCS
> buffers.
> [PATCH 06/12] i965/gen7+: Implement fast color clear operation in BLORP.
> [PATCH 07/12] i965/blorp: Expand clear class hierarchy to prepare for RT
> resolves.
> [PATCH 08/12] i965/blorp: Write blorp code to do render target resolves.
> [PATCH 09/12] i965/gen7+: Ensure that front/back buffers are fast-clear
> resolved.
> [PATCH 10/12] i965/gen7+: Resolve color buffers when necessary.
> [PATCH 11/12] i965/gen7+: Disable fast color clears on shared regions.
> [PATCH 12/12] i965/gen7: Enable support for fast color clears.
>

Forgot to mention: this series is avaiable on branch "fast-color-clear-2"
of git://github.com/stereotype441/mesa.git.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20130521/cee9c3a6/attachment.html>