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

[Emil Velikov]

Hi guys,

On 2 September 2015 at 20:10, Pohjolainen, Topi
<topi.pohjolainen at intel.com> wrote:
> 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).
Based on the discussion so far, I take it that it's unlikely that
we'll revert the commit at this point ?
Should we drop this patch for now ?

Thanks
Emil