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

[Matt Turner]

On Wed, Nov 25, 2015 at 1:21 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> 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.

You're right. I'll dig those out and take a look.