Lavapipe performance

[Jose Fonseca]

That's a relatively large geometry count.

llvmpipe (and consequently lavapipe) was optimized for desktop compositors
and UIs: large textured quads with blending, where most of the time is
spent in the fragment shader, particular texture sampling.

Not much effort went into optimizing llvmpipe for high geometry count --
for example, VS is not overlapped with FS.  At one point there was another
SW renderer gallium driver by a team at Intel that was specifically
optimized for huge number of primitives with no texturing (like the sort
used by https://vtk.org/ ), but I can't remember its name or find it.

Tiny triangles are also inefficient, because llvmpipe always runs 2x2 pixel
stamps, no matter if the triangle only covers a single pixel, plus blending
is always done in 4x4 pixels stamps.

Can you share a screenshot of what's being rendered to get a notion?

To make the most of llmvpipe ensure that:
- llvmpipe is using 8 (or 16?) threads (I believe using the number of cores
is the default, you can control this via `LP_NUM_THREADS:`)
- disable things that increase computation for minor visual enhancements,
like MSAA or anisotropic filtering
- make sure texture mag/min mipmap filters are the same
- avoid transparency
- privilege 32-bits rendertarget and texture formats like B8G8R8A8 /
R8G8B8A8

Jose


On Thu, Jan 30, 2025 at 12:15 PM George Karpathios <gkarpa1 at gmail.com>
wrote:

> Hi,
>
> I'm using Lavapipe (24.2.2, Windows 10) and trying to evaluate its
> performance, but I don't know if I can get more performance out of it or if
> I'm hitting its expected limits.
>
> For example, rendering a scene with ~300k triangles and ~150k lines, I get
> 5 fps on an i7 11800H (8 cores).  Of course I'm not expecting miracles but
> I was wondering if this is an expected performance range or if it should
> perform better.
>
> I have profiled it using VS's builtin tools, I'm getting some hotspots
> inside Lavapipe's dll, but I can't make any meaningful results by myself,
> or associate them with our code, in case we're doing something wrong that
> hurts the performance. I can't figure out what's normal and what's not, so
> if anyone would be willing to take a look at those, maybe someone can spot
> something out of the ordinary or provide some hints for me to understand it
> better and be able to continue, I would be grateful. I have uploaded a few
> screenshots at https://imgur.com/a/UvqwBzR . Thanks in advance!
>

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