[Mesa-dev] [PATCH] i965: Don't inline intel_batchbuffer_require_space().

[Chris Wilson]

On Tue, Nov 24, 2015 at 11:07:54PM -0800, Kenneth Graunke wrote:
> On Tuesday, November 24, 2015 05:17:29 PM Matt Turner wrote:
> > It's called by the inline intel_batchbuffer_begin() function which
> > itself is used in BEGIN_BATCH. So in sequence of code emitting multiple
> > packets, we have inlined this ~200 byte function multiple times. Making
> > it an out-of-line function presumably improved icache usage.
> > 
> > Improves performance of Gl32Batch7 by 3.39898% +/- 0.358674% (n=155) on
> > Ivybridge.
> 
> That's kind of sad.  When I added the render ring prelude code to this
> function, Eric was concerned about overhead like this.  I do wonder
> whether we'd be better off doing explicit ring switching, like I did
> on the 'ringswitch' branch of my tree.  That kills a bunch of the code
> on every BEGIN_BATCH().

Also note that I sent a bunch of patches earlier to remove the extra
code from BEGIN_BATCH and a ton of unnecessary work in relocation and
batch construction. In total there's about 20% (more on byt/bsw where we
couldn't emit batches fast enough to keep the GPU busy) on *Batch7.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre