[Mesa-dev] [PATCH 1/6] radeonsi: emit_db_render_state packets optimization

[Dave Airlie]

On 8 June 2018 at 07:53, Jiang, Sonny <Sonny.Jiang at amd.com> wrote:
> By applied patch 1, gfx IB size changes obviously.
>
>
> openarena GFX-IB-size changes from 7.64k to 7.44k.
> glxgears GFX-IB-size changes from 8.48k to 8.416k.
>
>
> The adding CPU workloads are quite small in this case and it's  hard to
> measure it. So the assumption is that writing a SET_CONTEXT_REG packet is
> more expensive. And we emit too many redundant packets. Some registers
> rarely get different values.

We spend a lot of time removing CPU overheads in draw call paths,  even threaded
it can still be something. This sort of idea can introduce a lot of
branches and cache
misses, reading a value back from the tracked_regs with a branch as opposed to
just writing directly to the DMA packet.

I think without a specified win for this code you aren't make things
better. it's
up to Marek and Nicolai, but I'm very wary of wasting time/energy in
this direction
without some numbers to show anything, good or bad.

Dave.