[Intel-gfx] patches for occlusion query fix on sandybridge

[Chris Wilson]

On Tue, 14 Dec 2010 20:59:09 +0000, david may <david.may10 at ntlworld.com> wrote:
> Hello Eric,
> 
> Tuesday, December 14, 2010, 5:58:58 PM, you wrote:
> 
> > Why don't we just keep all of our BOs LLC cached?  This was supposed to
> > be a big win of the new chipset, as it means we don't need to clflush.
> 
> Ohh,the implication here is that people are/have been writing the
> code,But Not bothering Actually benching/Profiling it to see if it actually is faster and
>  better throughput than before, that seems wrong, especially given sandy bridge is
>  supposed to be better, i Do Hope you are/will be testing/benching/Profiling
>   to see if it/all SB Code is actually  "a big win" one way or the other before passing for
>  release.

No, the default on SNB was changed back to uncached in order to fix some
coherency issues in the short term. Correctness first.

commit 8d0f56708292ca5c256ee3b7187d124afee81d93
Author: Zhenyu Wang <zhenyuw at linux.intel.com>
Date:   Tue Nov 2 17:30:47 2010 +0800

    agp/intel: restore cache behavior on sandybridge
    
    This restores cache behavior for default AGP_USER_MEMORY as
    uncached, and leave default AGP_USER_CACHED_MEMORY as LLC only.
    I've seen different cache behavior on one sandybridge desktop CPU vs.
    another mobile CPU. Until we figure out how to detect the real cache
    config, restore back to the original behavior now.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre