[Mesa-dev] [PATCH] Revert "i965: Stop aux data compare preventing program binary re-use"

[Pohjolainen, Topi]

On Thu, Aug 27, 2015 at 10:05:14AM -0700, Ben Widawsky wrote:
> On Thu, Aug 27, 2015 at 10:51:59AM +0300, Pohjolainen, Topi wrote:
> > On Wed, Aug 26, 2015 at 03:46:05PM -0700, Ben Widawsky wrote:
> > > This reverts commit 1bba29ed403e735ba0bf04ed8aa2e571884fcaaf
> > > Author: Topi Pohjolainen <topi.pohjolainen at intel.com>
> > > Date:   Thu Jun 25 14:00:41 2015 +0300
> > > 
> > >     i965: Stop aux data compare preventing program binary re-use
> > > 
> > > This fixes an intermittent failure in
> > > piglit.spec.arb_pixel_buffer_object.texsubimage pbo.sklm64 (maybe other
> > > platforms as well, but it is harder to reproduce). I can usually hit the failure
> > > within 10 runs of the test. This is a very hairy commit to debug. I'll let Topi
> > > handle it, or else we should go with the revert. I am open to either. I got
> > > lucky that Jenkins caught this on a run.
> > > 
> > > Here was the script I used for bisect:
> > > 
> > > i=0
> > > while [ $i -lt 40 ] ; do
> > >    ./bin/texsubimage pbo -auto -fbo > /dev/null 2>&1
> > >    [[ $? != 0 ]] && echo fail && exit 1
> > >    ((i++))
> > > done
> > > 
> > > exit 0
> > 
> > Should I use different piglit version than the current master? I'm asking
> > because I get this with both Mesa master and my patch reverted.
> 
> My piglit was pretty old. I just updated that, but mesa was master as of
> yesterday (output is below)
> 
> The one bit of advice I can add is that you make sure your system is updated to
> the very latest.
> 
> > 
> > testrunner at skl-y:~/topi/piglit$ ./bin/texsubimage pbo -auto -fbo
> > Using test set: Core formats
> > texsubimage failed
> >   target: GL_TEXTURE_2D
> >   internal format: GL_COMPRESSED_RGB_S3TC_DXT1_EXT
> >   region: 68, 12  32 x 48
> > texsubimage failed
> >   target: GL_TEXTURE_2D
> >   internal format: GL_COMPRESSED_RGBA_S3TC_DXT1_EXT
> >   region: 0, 28  116 x 20
> > texsubimage failed
> >   target: GL_TEXTURE_2D
> >   internal format: GL_COMPRESSED_RGBA_S3TC_DXT3_EXT
> >   region: 16, 4  60 x 36
> > texsubimage failed
> >   target: GL_TEXTURE_2D
> >   internal format: GL_COMPRESSED_RGBA_S3TC_DXT5_EXT
> >   region: 8, 0  104 x 60
> > Mesa: User error: GL_INVALID_OPERATION in glTexSubImage2D(out of bounds PBO access)
> > PIGLIT: {"result": "fail" }
> 
> Interesting. It so happens I have a patch that purports to fix some of these
> things. I did not try this patch myself for this issue.
> http://patchwork.freedesktop.org/patch/54025/
> 
> (I've been hanging on to this since I needed to do a bit of research to address
> Matt's feedback, specifically regarding render compression).
> 
> > 
> > 
> > Could you include the console output of the failure you get?
> > 
> 
> Here are two sample failures (occurred in 7 runs)
> 
> Using test set: Core formats
> texsubimage failed
>   target: GL_TEXTURE_2D
>   internal format: GL_INTENSITY
>   region: 27, 1  13 x 61
> Mesa: User error: GL_INVALID_OPERATION in glTexSubImage3D(out of bounds PBO access)

I got more and more a feeling that this is timing related. As the current
logic fails to ever re-use the items in the cache, the comparisons are
redundant and we can hardcode the search to always fail. This changes the
runtime dynamics closer to the patch being reverted:

diff --git a/src/mesa/drivers/dri/i965/brw_state_cache.c b/src/mesa/drivers/dri/
index f5f279c..746fe7b 100644
--- a/src/mesa/drivers/dri/i965/brw_state_cache.c
+++ b/src/mesa/drivers/dri/i965/brw_state_cache.c
@@ -224,6 +224,8 @@ brw_try_upload_using_copy(struct brw_cache *cache,
            continue;
         }
 
+         return false;
+
          if (cache->aux_compare[result_item->cache_id]) {
             if (!cache->aux_compare[result_item->cache_id](item_aux, aux))
                continue;


I can reproduce the error on IVB when I disable fast clears (I noticed that
the error is not SKL specific - it depends on the fast clears being disabled).